a long chapter of weary heart-breaking watchings, with an occasional half hour's work.

n Argo was the first object observed for purpose of delineation; after the first night's work little (and that by snatches) was done towards it, a new inroad of workmen and a long course of extremely unfavourable weather having carried the nebula out of convenient reach. The search, which was reluctantly given up, will, however, be again soon resumed.

I enclose two sketches, 4403 and 3570, of the 1864 catalogue. 4403. The horseshoe nebula is a grand object, conspicuous and with shape even in the finder (Plate I.). In the sketch the principal stars are laid down from measured position-angles about different centres; they are not as accurate as I could wish, and will be reobserved differently under better conditions; in no case, however, can there be sufficient error to influence in any material degree the configurations of the nebula or the smaller stars sketched in by eye.

It will be seen that the sketch contains considerably more detail than the corresponding figure in Herschel's Catalogue; there appears, however, to be no marked difference (with perhaps one exception) which may not be accounted for by the difference of aperture used.

The exception to which I allude is the presence of a small but conspicuous double star at the s. p. angle of the knot which lies between the 2 and the bright streak; the experiment has not been tried of cutting down the aperture to approximate to an 18-inch Herschelian, but the intrinsic brightness of the principal star, and the presence in the C. G. H. of stars not more bright (No. 3 of Herschel's catalogue is certainly less bright) go far to show, without this experiment, that the star did not exist as such with its present brilliancy at the time of the C. G. H. and P. T. 33 observations . . . I have not seen Mr. Mason's drawing, but look forward with much interest to examining it and his remarks thereon.

The important position of the star, and the careful scrutiny which the knot and its neighbourhood must have repeatedly undergone, forbid the assumption that it was simply overlooked by Sir John Herschel.

The star ẞ (I keep to Sir John Herschel's numbers and letters) is conspicuously and beautifully double, the companion of considerable brilliancy, about 15 mag.; with its present brilliancy and elongation it should, I think, be within reach of an 18-inch.

The knot is what I presume should be called resolvable; the appearance is sparkling, though no discrete stars can be seen, except perhaps a second faint one, which is suspected at the s. f. angle. Part of the streak near to the knot is also sparkling, but not in so marked a manner; the other portions appear of the ordinary milky nebulosity.

The fainter nebulosity (S) of the bright streak pretty well marks out the borders of the almost vacuous lane which leads up to and past the knot. On receding from the lane it becomes very faint: nor is this faintness uniform; but the appearances are so fugitive that, after repeated and painful

effort, I have been unable to catch them; the borders, however, stretching to the stars, as in the figure, are occasionally pretty well seen. On one or two occasions I have suspected the existence of a link between the nebulosity about the star No. 10 and the lower portion of the U; this, however, requires verification.

At the f. end the upper and smaller semicircle is plainly marked, the lower and larger very faint, and consequently its exact figure uncertain; there is certainly some very faint nebulosity leading through the groups of stars north of the three bright f. end stars, but it has not been added to the sketch on account of its uncertain figure and extreme faintness.

3570. A small but beautiful spiral. The two brighter knots are resolvable; the greater brightness of these knots is not particularly shown in Sir John Herschel's sketch (Plate I.), but is mentioned in the observations; the general ground is only slightly nebulous.

Of work out of the regular course, amongst other things, Neptune has been observed on some five or six occasions for figure and a second satellite, with only negative results.

In the absence of a photographic apparatus to be used at the uninterrupted focus of large mirror, attempts have been made to utilize the 2nd or Cassegrain image; an average exposure of near ten minutes on an eightday moon produced pictures which (by no means good) were of sufficient promise to make it worth while to resume the attempt under more favourable conditions.

The time of exposure is somewhat surprising, and would seem to accuse a great loss of chemical rays by a second perpendicular reflexion; but perhaps the more legitimate conclusion would be that the inactivity was mainly due to absorption at the surface of the large mirror, which was then very yellow.

The spectroscope arrived some time ago, but has not been much used; it is thought that for star work of any value some modification will be required, principally the exchange of the present collimator for one of longer focal length. A greater dispersion, moreover, seems desirable; for nebular work, however, for which it was mainly designed, the spectroscope in its present form, which is handy and compact, will be of much service.

For spectroscopic work on objects having a sensible diameter, the great telescope itself labours under some disadvantages; the enormous focal length and consequent magnification of the image is a serious inconvenience in the case of faint objects, and may be only partially remedied by a suitable condenser. This magnifying of the image may, however, in some cases be advantageous: I allude to the possibility thereby afforded of viewing small definite portions of moderately bright objects; unfortunately the objects with which we have to deal are seldom of such a character.

Of nebulæ, Orion has been examined for purpose of practice. The three lines are plainly and conspicuously seen; the hydrogen line is comparatively much fainter than I had anticipated, and disappears in the fainter

portions of the nebula. 30 Dorado shows the nitrogen line with facility; the second line certainly, but not in all positions, and always with difficulty; the hydrogen line is suspected only. I can see no trace of a continuous spectrum.

Argo has been observed on only one unfavourable morning; the nitrogen line was seen over a considerable space; of the presence or absence of others, or of a continuous spectrum, I am unable to speak with certainty.

With respect to future operations, it is intended that at first the routine work shall consist of a detailed delineation of the objects figured by Sir John Herschel, or any others which may prove interesting: this will take some time; for even without the impediment of cloudy weather, the delineation, with any degree of satisfactory correctness, of a moderately large nebula requires a considerable amount of work and careful and frequent scrutiny. It is hoped, however, that this work will by practice be found less painfully difficult than it is at present.

The spectroscope will be used as much as possible, the moon photographed, and attempts made to photograph the nebulæ, when a photographic apparatus has been procured, and staging, photographic room, &c. added to the building. It is, moreover, hoped that before long a refractor, of some nine inches aperture, may be procured, to be mounted with the reflector, or, preferably, as a separate instrument.

This telescope, besides being of much general use, will find much and valuable employment in determining micrometrically the chief points in the nebulæ under examination with the reflector, with more expedition and accuracy than at present; for spectroscopic work this telescope would be a valuable adjunct, especially if it be constructed of such comparatively short focal length as seems now to be practicable.

The great interest which the Royal Society has taken in everything connected with the Melbourne reflector is my sole apology for sending thus early such a meagre account.

February 24, 1870.

Lieut.-General Sir EDWARD SABINE, K.C.B., President, in the Chair.

I. "Note on certain Lichens." By JOHN STENHOUSE, LL.D., F.R.S., &c. Received January 10, 1870.

Through the kindness of W. Carruthers, Esq., of the Botanical Department of the British Museum, I obtained a considerable quantity of lichens from the neighbourhood of Moffat in Scotland. These were Cladonia rangiferina, and a mixture of Usnea barbata and Evernia prunastri,

the latter of which were carefully separated by picking-a somewhat tedious operation, as they were much interlaced.

Usnea barbata.

In order to extract the usnic acid from this lichen, it was macerated for about thirty minutes with a dilute solution of sodic carbonate, squeezed, again treated once or twice in a similar manner, and the turbid solution precipitated by a slight excess of hydrochloric acid. The crude dark-green acid thus obtained was mixed with milk of lime and a considerable quantity of warm water (40° C.), filtered, and the clear lemon-coloured solution of usnate of calcium acidulated with hydrochloric acid. The acid was thus precipitated in pale yellow flocks, which were collected.

*

The reason that I adopted this modification of the process I formerly proposed is, that although usnic acid readily dissolves in milk of lime when it has been extracted, yet in order to exhaust this and other compact lichens, it requires to be treated a great many times if lime be employed, whilst two or three are sufficient with carbonate of sodium.

The partially purified usnic acid obtained in the manner above described was easily rendered quite pure by taking advantage of the peculiar property which this acid possesses of forming an insoluble calcium salt when boiled with lime. The crude yellow acid was placed in a flask with a quantity of water and an excess of slaked lime, and the mixture boiled for twenty minutes or half an hour. The insoluble calcium usnate was collected, well washed with hot water, and the lime then removed by boiling it with a slight excess of hydrochloric acid. The tolerably pure usnic acid was then collected, and well washed with boiling water. It was advisable to continue the digestion with hydrochloric acid for half an hour, as it rendered the acid more compact and easy to collect. By this alternate treatment with lime and acid, a large quantity of some dark-coloured impurity was removed. This forms the best process for recovering usnic acid in a state of tolerable purity from residues.

It was found, however, to be better, when considerable quantities of usnic acid were to be prepared, to boil the pale yellow usnic acid paste, as obtained by precipitation from the lime solution, with a small quantity of water, to which strong caustic soda solution was gradually added, sufficient to dissolve nearly the whole of the usnic acid. It was then set aside to crystallize, and when cold the very dark coloured supernatant mother liquor decanted, and the crystals of sodic usnate washed once or twice by decantation, with a small quantity of cold water. It was then redissolved and recrystallized once or twice in the same manner.

The nearly pure sodic usnate was now dissolved in a considerable quantity of hot spirit, filtered, and the boiling solution strongly acidulated with acetic acid. The usnic acid then separated in fine needles, which when cold were collected, well washed with cold spirit (in which they are almost * Ann. der Chem, und Pharm, vol. Ixviii. p. 98.

insoluble), and recrystallized from boiling spirit to render them quite

pure.

When the quantity of acid operated on was but small, the best process was to dissolve it, by means of caustic soda solution, in a large quantity of boiling spirit, filter from the insoluble impurities, and strongly acidulate with acetic acid. The nearly pure usnic acid, which crystallizes out in large needles when the solution cools, was collected, washed, and recrystallized two or three times from spirit.

I. 130 grm. usnic acid gave 298 grm. carbonic anhydride and 060 grm. water.

II. 245 grm. usnic acid gave 564 grm. carbonic anhydride and 188 grm. water.

I.

II.

C13

= 216 = 62.43

62.53

62.79

Hesse. 62.80

= 18 = 5.20

5.13

4.99

5.00

0, = 112 = 32.37

I. was purified by boiling with lime, and II. by repcated crystallization of the crude acid from spirit.

In the analyses published by W. Knop, Rochleder, and Heldt, and also by myself in 1848, the carbon is about 75 per cent. higher than the above, and the formula deduced from it was C1, H1,O,. Hesse* from his analyses proposed the formula C1, H1, O,, which I have adopted.

18

19

16

Usnate of Sodium.

This was best prepared by adding one part pure usnic acid to twenty of boiling water, and then sufficient caustic soda solution to dissolve nearly the whole of the acid, filtering, and setting aside to crystallize.

After one recrystallization it was subjected to analysis.

I. 598 grm. usnate of sodium gave 114 grm. sulphate of sodium. II. 864 grm. usnate of sodium gave 168 grm. sulphate of sodium.

This salt crystallizes in pale yellow silky needles, is not very soluble in cold water, but more so in spirit. It is readily decomposed by carbonic anhydride; so much so, that when pure sodium usnate is exposed for some time to the atmosphere, it absorbs carbonic acid, and is no longer completely soluble in water. By passing a current of carbonic anhydride through its aqueous solution, the usnic acid is entirely precipitated.

* Ann. der Chem. und Pharm. vol, cxvii. p. 345.