In the above table, the angles of disappearance and reappearance are given from the Apparent North (the real south) point of the Moon's Limb, as seen in an inverting telescope, or that intersected by a circle passing through the North Pole, and the centre of the Moon's image; or from the point of intersection of the Moon's Limb by a circle passing through the zenith, and the Moon's centre, this latter angle (that from the Vertex) being useful where the observer's telescope has only an altazimuth mounting. These angles in each case are measured to the right, completely round the Moon's Limb, i.e., supposing we are viewing the Moon with the naked eye, from South, round by East, North, and West, to South again. In the column headed "Moon's Limb," however, in the case of near approaches, we have indicated the true point of the Moon's Limb which will approach most nearly to the Star; in order that the observer may determine how far it is possible or probable that the Greenwich near approach may become an Occultation at his station. Thus, in the evening of January 21st, we see from the table that the S.S.W. limb of the Moon, as seen from Greenwich, will pass close to 14 Virginis. Hence it must be evident that anyone situated sufficiently far to the N.N.E. of Greenwich, will see the Moon actually occult this star. Mercury Jupiter Is an Evening Star, but is rapidly approaching 30.3 6 52.2 4 46.1 Right Declination 11 0.0 7 16.8 3 17.3 7 18.9 Is a Morning Star up to the Day of Month. h. m. h. m. 21 0 51.1 4 10.2 11 1.4 a.m. 26 0 53.9 4 28.9 5 3.5 "" 11 14.9 31 0 56.9 4. 48.8 4 12.8 11 29.4 29 24 14.0 16 19 28.6 23 37.9 21 20 3.9 22 25.2 26 20 39.4 20 34.5 31 21 14.8 18 5.2 It will be seen from the above ephemeris that the path of Mercury this month, described in the immediate neighbourhood of the Sun, starts from Ophiuchus, and carries the planet through Sagittarius into Capricornus. III 3 EELE Satellite. I Tr I 10 I Oc D བབབ 21 III Sh I Sh E III Ec D Tr E III II Sh E 10 20 Ec Eclipse; Oc Occultation; Tr Transit of Satellite; Sh Transit of Shadow; D Disappearance; R Reappearance; I Ingress; E Egress. The printing of a phenomenon in italics indicates that its visibility is rendered doubtful, either by the brightness of the twilight or by Jupiter's proximity to the horizon. a Persei y' Eridani Aldebaran Capella Rigel a Leporis a Orionis μ Geminorum = .. .. 555.04 "" 9 42 26-43 39 10 21 9.44 "" 10 22 3-33 99 10 40 40-09 11 1 51.65 99 11 28 49-42 99 Sirius .. 11 52 59.62 Castor 12 39 52.63 "" Procyon 12 45 55.15 "" As the Stars, supposing them to be absolutely fixed, would South 3m. 55.918. (or 235 91 seconds) sooner every day, we have only to multiply this quantity by the number of days which have elapsed since the beginning of the month-i.e., by the number of the day of the month-1, and subtract the result from the time given above, to obtain the time of Meridian passage of either of the Stars in the above list for any other night in January. Thus supposing that we wish to know the Greenwich Mean Time of Transit of a Ceti on the night of January 11th. Then 111 10 and 10 X 235-91s. 2359-1s., or 39m, 19-1s. Taking this from the quantity given in the table, 8h. 9m. 39-08s., we finally get 7h. 30m. 1998. as the Greenwich Mean Time. of Southing of a Ceti on the night of January 11th, a result just 0.11 second in excess of the precise instant of Transit of the star in question on the night referred to. The times given in our Table are absolutely correct to the nearest hundredth of a second. The rule just given does not apply with quite equal accuracy to Polaris, or any close circumpolar Star, but it does so quite sufficiently for all practical purposes. If we wish to find our Local Mean Time of Transit of either of the Stars in this List, we may do so by taking 9-8565 seconds from the time given in the table for every hour of Longitude (and proportional parts for minutes and seconds) when our station is to the West of Greenwich; and adding the same quantity when it is to the East of that Meridian. For example, what will be the Oxford Mean Time of Transit of Aldebaran on the night of January 1st, 1881? Oxford is 5.05m. West of Greenwich. Then we say 60m.: 5.05: 9.8565s.: 0.83s. Subtracting this then according to our precept from 9h. 42m. 26 43s., we get 9m. 42m. 25-60s., as the Oxford Mean Time of Southing of Aldebaran on January 1st. Had our supposed station been 5.05m. East of Greenwich, the 0.33s. must have been added. BULLOCH'S NEW BIOLOGICAL MR The accompanying figure shows the instrument about two fifths actual size. When vertical it is 12 and a fin. high, and the stage is 3 and a tin. from the table. The body-tube is 5in. in length, and the draw-tube is marked at the position of standard length. The limb is supported on an axis that permits inclination | from the vertical to the horizontal, and that can be clamped to two thick metal jaws that form the upper end of the single pillar attached to the base plate. The coarse adjustment is by rack and pinion, and extra V-shaped slides fit into corresponding grooves on either side of the rack-work to secure steady motion. an fixes it. The substage and mirror are each fitted to swing laterally (independently or together) concentric with the object on the stage; they both swing from the axis to considerably above the stage (for "opaque" illumination) ou an axle passing through the lower part of the limb, and they can be clamped by the milled head shown behind the pillar. The angle of inclination can be read by graduations on the cylindrical edges forming the upper ends of the swinging bars. The substage slides nearer or farther from the stage, and can be centred. The conical piece shown in the figure is a diaphragm, that can be pushed up in contact with the base of the The fine adjustment is of Mr. Bulloch's object; it fits into the substage by the "Society" special design, consisting of a box-fitting, carry- screw, from which it can be removed and an ing the large milled heads and toothed pinion, objective substituted as a condenser. If, for this on which controlled by a a straight pinion acts beneath latter purpose, the body of the objective is extra lever suspended on long, the substage can be reversed-thus giving axle, the whole concealed in the broad nearly an inch of additional space. part of the limb; this lever is itself acted upon by the fine screw shown on the back of the limb. The downward motion of the screw presses down the lever, the other end of which forces up the straight pinion acting on the box-fitting, which is itself pressed downwards by a strong spiral spring fitted above it in the hollow limb, thus a range of about 1-6io. is allowed for the fine adjustment. Strong metal cheeks are placed on either side as guide-pieces to prevent rocking motion, while the friction they produce is imperceptible, in consequence of the downward force exerted by the spiral spring. with a broad-gauge screw, termed in America The optical body is fitted at the lower end the Butterfield gauge," which is found important when low-power objectives of very large aperture are employed. Some of these objectives, as made in America, have back lenses so large that the " "society gauge cuts off part of the aperture-hence the large gauge adopted. The usual "society" screw is applied as an adapter. The mirror-arm slides on a grooved fitting, and can also be drawn out of the tube-fitting. By swinging aside the substage the mirror (plane or convex) can be used alone at any angle. By placing the microscope horizontal, the mirror can be removed from the tube-fitting and its place taken by a small candle; used in conjunction with a condenser applied in the substage, this plan of illumination will then be found very effective for obtaining obliquity: both radial arms can then be moved togethera slight spring-key holding them together. The precise axial position is also found by the action of spring-keys slightly locking the moving arms when they are in the axis. Bulloch also supplies the sliding glass frictionBesides the stage shown in our figure, Mr. stage-much used in America-or a stage with mechanical motions that appears to be of simple and efficient construction. These points we are enabled to note from an excellent photograph and from section drawings sent to us by Mr. Bulloch. We understand this microscope will be exThe stage is fitted to the limb by an angle-hibited at the next meeting of the Royal Micropiece and is provided with rotating and contring scopical Society, on January 12, by Mr. Frank motion; a clamping-screw, shown in front, Crisp (secretary). OPTICS WITH THE LANTERN.-V. ARRANGE the lantern and prism as in Fig. 8. Article III., the prism a little beyond where the rays from the lantern cross. I would just say here that a bisulphide prism is incomparably superior to glass for these experiments, giving at least double the dispersion; and two are necessary for some things; but a spare prism or other apparatus can often be hired or borrowed by those known to be capable of properly using them, and I have frequently been indebted to others in this way for some particular experiment. By turning the prism on its axis, a position will soon be found in which the lantern-beam is least deflected: this will be found to be when the entering and emergent beam (as the angles differ with the different colours, it is usual to measure the yellow ray as both a medium position and the most luminous) are inclined to their respective faces of the prism at similar angles. But now notice that, on rotating the prism in one direction from this position, the ray is not only more refracted, but more dispersed the spectrum lengthened, particularly at the violet end. In the other direction, while the refraction also increases, the spectrum is shortened. Now I do not want to go into optical calculations here; but in this fact the student will readily see why different combinations of single or non-achromatic lenses, to a great extent, may be arranged to correct both chromatic and spherical aberrations-a point I have found to puzzle many people. For it is evident that the effects of three prisms, A, B, C, of equal angles variously inclined, as in Fig. 1, to four quarters. On each of these, paint in clear water-colours, as nearly as you can in the proportions of the spectrum, the seven spectral colours. You will not get them very correct at first, and it may be best to purchase the "Newton's disc," as it is called, of an optician; but many of them are too dark in the blue division. This is to be mounted so as to be rotated by a cord and simple multiplying arrangement, and then adjusted towards the screen facing the lantern, so that the light may be just about concentrated upon its face when the focussing lens is run fully out. If the disc of light is too large, put a circular aperture, cut in a black card, which will sufficiently reduce it, in the optical stage. This is important, for this fine experiment often fails because carried out by gives very poor effect; whereas the full beamthe general gas-light of the lecture-room, which from the lantern brought on the face of the disc in a dark room appears very differently. Now rotate the disc rapidly, and we get white more or less bright or greyish, according to the correctness of the proportions. Newton's disc can also be purchased as a glass slide for the ordinary stage of the lantern, and shows very perfectly in this way, but it is inferior to the painted card for the next experiments. We see, either way, that the presentation of a proper assortment of the colours to the eye, anyhow, produces white. Cut out from a circle of blackened paper, the size of the disc, radial sectors so arranged as to cover the same colours in each quadrant-say, the violets and blues-and fix them on the disc by a drawing-pin at the end of each. We thus suppress colour; and, as before, we get colour. Again prepare a disc of stiff, blackened card, as in Fig. 6, with two radial slits each 24in. long, and, say, in. wide. Run a drawing-pin through the centre into the end of a stick, so that it can be rotated by the finger like a child's windmill, and hold the affair, or fix the stick in a clamp if you like, so that each slit in rotating will cross the nozzle of the lantern and so let a flash of light through. (This rough-and-ready plan does just as well as more finished apparatus). Let an assistant rotate the disc as before, and get a good white. Now introduce your black disc and rotate that with the fore finger. The brief flashes prevent all the colours from now reaching the eye during one period of visual impression, and so again you virtually suppress more or less colour. And again, therefore, you get colour, its character and amount depending on the respective rates of rotation. Yet another experiment on the spectrum itself. Arrange the prism P as before in front of the nozzle, but with the reflector R so in the path of The reflector must turn very easily in another vertical socket. Give a rapid rocking motion through a small arc to the reflector, which will, of course, move the spectrum backwards and forwards across the screen. Begin slowly, and you see that the motion in no way changes or modifies the colours. But when the motion becomes rapid, the spectrum becomes white over all the middle portion, colour being only visible towards the ends, where all the colours cannot of necessity be made to fall. The reason is the same as with Newton's disc, and, of course, if we stop off any of the coloured rays which fall on the mirror, by taking them away we again get colour. Finally, we can see from this that to get a pure spectrum, or pure colours, we must use a narrow slit. For cut apertures in one of the black cards, as in A, Fig. 8, the larger one being FIC.8 B W. (5) All Cases of really superior or complete Design should possess a Plinth,-in appearance; but the actual structure of the latter will be governed by circumstances, as is sufficiently indicated in the present Six Instructions. n. The foregoing method has only the disad- if money be scarce, such a dispensation will be vantage of involving a little extra work, and of preferable. It is, of course, to be understood requiring great nicety to insure that the Pipes that the Instrument is here assumed to be either shall appear exactly regular. Still, with care, Stationary or on a Platform. such accuracy can be attained. A very good method is to first make the lower or inside Stay as a simple plain Bar, following the backs of the Pipes; and then to prepare, for each Pipe, a short Piece of thin Stuff (say Deal), having a semicircle cut in it-at one of its end-grain ends corresponding with the plan-section of the said Pipe: then each of the latter will be put into its precise final position, and the prepared Piece be brought to and adjusted in its exact place by the Pipe; finally, the Piece will be firmly affixed to the Bar. By these means the semicircular Cuttings will not be liable to break into each other; and perfect symmetry of appearance may be secured for the Pipe portion of the Front. 0. The preceding Treatment may always be adopted when it is necessary to remove the Show Pipes for the purpose of Tuning. When such removal is not required. one Stay will suffice, it, of course,carrying the Semicircular or Segmental Cuttings. If this Stay be Visible the Pipes will be attached to it by means of Tape Ties: if it be Invisible it will be furnished with Stout Wires, and each Pipe will be provided at its back with an Eye or Loop, which will hook over on to the said Wire. 0.0. An Example of the Visible Stay occurs in the Hoddesdon Organ, already (as at y. y, ante) mentioned: a Specimen of the Invisible will be found in the. Instrument by Fincham, in the Parish Church of Egerton, Kent. about fin. square. It will be obvious that the spec- workman, &c., through a Door in the lowest x. (6) All Organs which are entered by the part of the Case, should have the Case-Plinth, if present, so constructed that the corresponding portion of it is removed along with the said Door. By this means the person entering will not have anything to step or stumble over; and the already mentioned (at 76, f)-will be avoided. unpleasant worn appearance of such portionThis No. 6 can, of course, be carried out only when the Instrument is either Stationary or set on a Platform. XX. A good Example of a Case made withou a Plinth occurs in the Hoddesdon Organ,— already (as at yy ante) several times mentioned. * STRUCTURE. See first with reference to a Sliding Pedalboard, at n and o next. Runners without a Platform, the Plinth should y. General. Whenever the Organ is on take the form of a complete strong and secure Framing, for it will in such event-whether a separate Building-frame be or be not presenthave to carry the entire, or at any rate the greater portion, of the Case, and this, remember, at clear of the ground. Any Set-In portion of such Plinth (such as that into which the Pedal-board frequently enters) should, if possible, be continued as a straight plain part running behind the Projecting portion of the same Plinth until it meets, and can therefore be keyed into, the side of the latter: or sometimes twoSet-In divisions occupying the end (side) portions of a Plinth-Front may in reality consist of q. The shape on Plan of the Stay will, of one straight Piece, which passes behind the centhat the Face of the Curtain or other compart-firmly keyed at each end into the Side proper of course, depend upon what Plan line it is desired tral advanced division of the Plinth, and is ment shall follow. See TREATMENT ON PLAN the same Plinth. The object of this treatment (52, h); also CURTAINS (68, j). is simply to prevent the weakening of the Plinth, which might otherwise result from the Breaking of its Plan Outline by the aforesaid Setting-In. See also with reference to having the Plinthfront to be wholly straight under some circumstances (i, next). Stays. Thickness.-This will be found -pricked to 11-pricked, or sometimes thicker than even this last. ** PLINTH. (68, ); and with reference to Toe-butt and yy. A very firm Specimen of a Runnered Plinth occurs in the small Organ at Christchurch Vicarage, Ware, Hertfordshire (see 58, y). Before going on to the rainbow, achromatism, absorption, and the subjective or purely sensational nature of colour, it may be well to mention an optical black varnish. I had a deal of trouble in blackening cards, &c., until a practical optician gave me his recipe, which consists simply of vegetable black, mixed with French polish more or less diluted with methylated spirit. This can be prepared in an instant, qq. The Plinth is the lowermost Member of dries rapidly, and is alike suitable for cards, the Case proper, and forms a more or less pro-which stand on a complete Platform to which z. In all Organs which are stationary, or metal, or the large pressure-boards for a gas-jecting Base to the entire Composition,bag. It is a good black, and does not come off. already been shown under Head of DESIGN itself the Wheels are attached, the foregoing (54, k). method of constructing the Plinth is not of course obligatory; but still, if the Instrument benot large enough to admit the ingress of the Tuner, &c., to the lower portion of the Case, it will usually be better to make the Plinth in a complete Framing of some sort. THE ORGAN: A COMPREHENSIVE * NECESSITY FOR. -as has r. The necessity for a Plinth being included as one of the component portions of the Organ Case will depend to a great extent on individual circumstances. There will be instances in which the Plinth may be regarded as indispensable, and there will be others under which such a Construction would be only in the way. A few words must therefore be given on these points. BY this is meant any horizontally or otherwise The following condensed Directions will, I [79, a.] In all three preceding paragraphs it has been assumed that the Plinth is existent. throughout the whole of the Case-Front; that is to say, that there is no cessation of such Plinth at the portion of the Case which is beneath the Manual Keys. It has already (at 7 7, ante) been seen that the Plinth is always more or less Pros. (1) All Organs which are placed on Run-jectant from the Body of the Case; therefore it. 1. A Visible Pipe-stay should as a rule always ners (see 46, v), and yet have no Platform (see will easily be understood that, ordinarily, such form part of the Case-Design. Such a Stay may 46, z), should have their Cases possessing a Projection follows faithfully the Plan-outline be made to much help the appearance of the regular framed Plinth of strong formation. exhibited by that portion of the Case which rests Composition, and will also, if treated in a certain t. (2) All Chamber Organs should as a rule be upon the Plinth. It is now to be observed that way, facilitate the removal of the Show Pipes placed either on Runners or on Wheels (see should it be found a matter of importance to set (see next parag.): it likewise furnishes a safe-16, ), and will, therefore, unless a Platform be the Pedal-board as far back under the Manuals guard against the Pipes being able, under any present, come under the conditions of No. 1 pre-as is possible, or should it be desired to save the circumstances, to fall outwards. See also in ceding. slight waste of plan-space manifestly entailed by Department of GENERAL LAY-OUT, with reference not having the Lower-Door set vertically over to the Slinging of very large Show Pipes; and the Plinth, such a setting of the said Loweras to the necessity for veiling such Sling. Door may be safely permitted:-that is to say, such Door may be placed so that its front face is either actually flush with or only slightly set back placed BAR to which the larger Pipes are think, be found sufficient for all occasions. Hooked or Tied. m. The most convenient treatment for the u. (3) All Organs which are large enough to receive and contain sufficient space for the admission of the workman's person at a number of points between the Building-frame and the Case supporting of the Show Pipes is to have them closely set against the front or visible Stay; and (such an Instrument will almost invariably be from the front face of its corresponding portion then to place, at a little below the latter and of course behind the said Pipes-a second Stay, segmented out so as just to fit them. Thus on drawing the Pipe forward by means of its Foot, its Body becomes directly freed, and the entire Pipe can be then taken out without difficulty or damage. All rights reserved. Platform), may receive a Case Plinth; but it is v. (4) All Cases, the Bases of which are little making coincident or nearly coincident may be done either by bringing the Lower-Door forward, or by increasing the amount of the setbackward of the [central] portion of the Plinth Front. The first-named of these treatments is usually, in the abstract, the preferable one; but as it is essential that the Set-back of such central portion of the Case-Body be never sacri of the Plinth. It will be obvious that such a b. There is sometimes an additional reason why there should be no sacrifice of the Break at the portion of the Case which is between the Plinth and the Impost; and this is, that it is frequently desirable, when plan-room is scarce, that the Plinth itself should not be given much Projection from the main body of the Case, and therefore that such Projection or Breaking becomes more necessary at the remaining parts: see more fully in DIMENSIONS (80, d). ficed (except under very extraordinary circum-spect to the interpretation of these facts two series of forms has come to light, they illustrate stances), such a bringing forward of the Door is to hypotheses, and only two, appear to be imagin- the three-fold law of evolution as clearly, though, so strikingly, as the equine be permitted only when the Set-back of the able. The one assumes that these successive forms perhaps, not does. Carnivores, artiodactyles, and latter from the Sides or Towers of the Front of equine animals have come into existence inde- series pendently of one another. The other assumes periosodactyles all tend, as we trace them exceed in amount the extent of the Set-back of that they are the result of the gradual modification back through the tertiary epoch, towards less itself (the Door) from the Plinth,-in which undergone by the successive members of a con-modified forms, which will fit into none of the latter case the Door will, of course, reach the tinuous line of ancestry. As I am not aware that recognised orders, but come closer to the insectiFront of the Plinth, while yet the said sides any zoologist maintains the first hypothesis, I do vora than to any other. It would, however, be remain beyond the Door, and so the Plan break not feel called upon to discuss it. The adoption most inconvenient and misleading to term these between Sides and Door will be maintained. See of the second, however, is equivalent to the primordial forms insectivora, the mammals soalso with g next. acceptance of the doctrine of evolution so far as called being themselves more or less specialised horses are concerned, and, in the absence of modifications of the same common type, and only, evidence to the contrary, I shall suppose that it is in a partial and limited sense, representatives of accepted. Since the commencement of the eocene that type. The root of the matter appears to me epoch, the animals which constitute the family of to be that the palaeontological facts which have the equida have undergone processes of modifica- come to light in the course of the last ten or fifteen tion of three kinds:-1, there has been an excess years have completely broken down existing taxoof development of one part of the oldest form over nomical conceptions, and that the attempts to conanother; 2, certain parts have undergone complete struct fresh classification upon the old model are or partial suppression; 3, parts originally distinct necessarily futile. The Cuvieran method, which have coalesced. Employing the term "law" all modern classifiers have followed, has been of simply in the sense of a general statement of facts immense value in leading to the close investigation ascertained by observation, I shall speak of these and the clear statement of the anatomical characters c. Whenever an Organ is large enough to three processes by which the eohippus form has of animals. But its principle, the association into allow of the free entry of a person into and about passed into equus as the expression of a three-fold sharp logical categories defined by such characters, its lower portions (such an Instrument will faw of evolution. It is of profound interest to was sapped when Von Baer showed that, in estialways be too extended in area, &c., to receive remark that this law, or generalised statement of mating the likenesses and unlikenesses of the Runners, except with the addition of a Plat- the nature of the ancestral evolution of the horse, animals, development must be fully taken into form; see Department of BUILDING-FRAME) it is is precisely the same as that which formulates the account; and if the importance of individual denot recommended ever to have its Plinth made process of individual development in animals velopment is admitted, that of ancestral developin a separate complete framing. The first reason generally, from the period at which the broad ment necessarily follows. If the end of all zoofor this is because such framing is in no wise re-characters of the group to which an animal belongs logical classification is a clear and concise expression are discernible onwards. After a mammalian of the morphological resemblances and differences quired, for either a Kerb or a Kerb-Platform embryo, for example, has taken on its general of animals, then all such resemblances must have a (see 72, k) ought in all such instances to be pre-mammalian characters, its further progress towards taxonomic value. But they fall under three heads: sent. The second reason is because of the its special form is affected by the excessive growth (1) those of adult individuals; (2) those of sucbulkiness of the single Piece which is then re- of one part or relation to another, by the arrest or cessive stages of embryological development or sultant. The third reason is that for a person to suppression of parts already formed, and by the individual evolution; (3) those of successive stages be able to enter the Organ he would then gene- coalescence of parts primarily distinct. This coin- of the evolution of the species, or ancestral evolurally have to pass over the Plinth, and this cidence of the laws of ancestral and individual tion. An arrangement is " "natural," that is, necessity, besides its inconvenience, must often development creates a strong confidence in the logically justifiable, exactly in so far as it expresses lead to the injury of the appearance of this por- general validity of the former, and a belief that the relations of likenesses and unlikenesses enution of the Case; for Tuners and other per- from the known to the unknown. The astronomer to classify the mammalia, we must take into ac we may safely employ it in reasoning deductively merated under these heads. Hence, in attempting sons will sometimes persist in stepping on instead who has determined three places of a new planet count not only their adult and embryogenetic of over the Plinth, and the upper edge of the circulates its place at any epoch, however remote; characters, but their morphological relations, in so latter, therefore, soon begins to show the effects and, if the law of evolution is to be depended far as the several forms represent different stages of their foot-marks. The fourth reason is that upon, the zoologist who knows a certain length of of evolution. And thus, just as the persistent it is exceedingly convenient-when the Pedal- the course of that evolution in any given case may antagonism of Cuvier and his school to the essence board is not movable-to lengthen the Checks with equal justice reason backwards to the earlier of Lamarck's teachings (imperfect and objectionable of the Pedal-Frame so as to enable them to carry but unknown stages. Applying this method to as these often were in their accidents) turns out to the Composition-Pedal Bearings; and the pass-the case of the horse, I do not see that there is any have been a reactionary mistake, so Cuvier's no ing of these Cheeks through the Plinth of course ceded by mesozoic forms, which differed from the present day, the existence of a reason to doubt that the eocene equidæ were pre- less definite repudiation of Bonnet's "échelle" at "scala anieohippus in the same way as eohippus differs from mantium," is a necessary consequence of the docequus. And thus we are ultimately led to con- trine of evolution, and its establishment constitutes, ceive of a first form of the equine series, which, if I believe, the foundation of scientific taxonomy. the law is of general validity, must need have been Many years ago, in my lectures at the Royal provided with five sub-equal digits on each planti- College of Surgeons, I particularly insisted on the grade foot, with complete, sub-equal antebrachial central position of the insectivora among the and crural bones, with clavicles, and with, as at higher mammalia; and further study of this order present, 44 teeth, the cheek-teeth having short and of the rodentia has only strengthened my conMoreover, since Marsh's investigations have shown range of string is crowns and simple-ridged or tuberculated patterns. viction that any one who is acquainted with the that the older forms of any given mammalian possesses the key to every peculiarity which is met group have less developed cerebral hemispheres with in the primates, the carnivora, and the unguthan the later, there is a prima facie probability lata. Given the common plan of the insectivora that this primordial hippoid had a low form of and of the rodentia, and granting that the modifibrain. Further, since the existing horse has a cations of the structure of the limbs, of the brain, could not have presented a higher, and may have which occur among them may exist and accumudiffuse allantoic placentation, the primary form and of the alimentary and reproductive viscera possessed a lower, condition of the various modes late elsewhere, and the derivation of all eutheria by which the foetus derives nourishment from the from animals which, except for their diffuse plaparent. Such an animal as this, however, would centation, would be insectivores, is a simple deducfind no place in any of our systems of classifica- tion from the law of evolution. I venture to extion of the mammalia. It would come nearest to press a confident expectation that investigation into the lemuroidea and the insectivora, though the the mammalia fauna of the mesozoic epoch will, non-prehensile pes would separate it from the sooner or later, fill up these blanks. Professor former, and the placentation from the latter Huxley proceeded to give details on which his conProfessor Huxley began by saying:-There is group. A natural classification is one which clusions were based, and dwelt on the fact that evidence the value of which has not been disputed, associates together all those forms which are much careful work is needed to clear up problems and which, in my judgment, amounts to proof, closely allied and separates them from the rest. before us. that between the commencement of the tertiary But, whether in the ordinary sense of the word epoch and the present time the group of the "alliance," or in its purely morphological sense, it equida has been represented by a series of forms, is impossible to imagine a group of animals more A SIMPLE SINGLE-ACTING STEAMof which the oldest is that which departs least from closely allied than our primordial hippoids are the general type of structure of the higher with their descendants. Yet, according to existing mammalia, while the latest is that which most arrangements, the ancestors would have to be widely differs from that type. In fact, the earliest placed in one order of the class of mammalia and HE great bugbear staring the amateur mechanic known equine animal possesses four complete their descendants in another. It may be suggested small steam-engine is the matter of boring the sub-equal digits on the fore foot, three on the that it might be as well to wait until the primor-cylinder. To bore an iron cylinder on a foot lathe hind foot; the ulna is complete and distinct from dial hippoid is discovered before discussing the is difficult, even when the lathe is provided with the radius; the fibula is complete and distinct from difficulties which will be created by its appearance. automatic feed gear, and it is almost impossible the tibia; there are 44 teeth, the full number of But the truth is that that problem is already with the ordinary light lathe possessed by most canines being present, and the cheek-teeth having pressing in another shape. Numerous "lemurs," amateurs. To bore a brass cylinder is easier, but short crowns with simple patterns and early- with marked ungulate characters are being dis- even this is difficult, and the cylinder, when done, is formed roots. The latest, on the other hand, has covered in the older tertiaries of the United States unsatisfactory on account of the difficulty of adaptonly one complete digit on each foot, the rest being and elsewhere; and no one can study the more ing a durable piston to it. The engravings show a represented by rudiments; the ulna is reduced and ancient mammals with which we are already simple steam-engine, which requires no difficult partially anchylosed with the radius; the fibula is acquainted without being constantly struck with lathe work; in fact the whole of the work may be still more reduced and partially anchylosed with the the insectivorous characters which they present. done on a very ordinary foot lathe. The engine is tibia; the canine teeth are partially or completely In fact, there is nothing in the dentition of either necessarily single-acting, but it is effective neversuppressed in the females; the first cheek-teeth primates, carnivores, or ungulates, which is any theless, being about 1-20 H.P., with suitable steam usually remain undeveloped, and when they supply. It is of sufficient size to run a foot lathe, appear are very small; the other cheek-teeth have scroll saw, or two or three sewing machines. The long crowns, with highly complicated patterns and late-formed roots. The equidse of the intermediate ages exhibit intermediate characters. With re tends to weaken the latter. (To be continued.) PROFESSOR HUXLEY ON EVOLUTION. A the of years ago. means of deciding whether a given fossil skeleton, ENGINE.* TH in the face when he contemplates making a From the Scientific American. |