As the very existence of the press depends on popularity this is inevitable, but it none the less throws a great reponsibility on those who possess this popularity if they mislead public opinion by inaccuracy or suppression of facts.

In his article on "Fallacies of Testimony" Dr. Carpenter, quoting Schiller, says, that the "real philosopher" is distinguished from the "trader in knowledge" by his always loving truth better than his system. If our readers will carefully weigh the facts now laid before them, they will be able to decide how far Dr. Carpenter himself belongs to the first or to the second of these categories.

ALFRED R. WALLACE.

Text-Book of Structural and Physiological Botany. By OTTO W. THOME. Translated and Edited by ALfred W. Bennett, F.L.S. London: Longmans and Co.

We have here a translation of a German work which has found great approbation in its own country, and will probably experience an equally favourable reception in England. It embraces the whole range of elementary botany, and will prove a safe and convenient guide for the student in the earlier part of his career. The Editor, however, very judiciously reminds his readers that in Natural Science "the greater and the most useful part of the student's knowledge must always be acquired in the field, or with the dissecting knife in hand," the use of text-books being merely to put him in the right track for personal research, and to save him from the necessity of re-discovering what others have already

"You on your part shall undertake that during the period of the sittings, and for one week afterwards, you will neither take, nor cause to be taken, nor countenance legal proceedings against him or me.

"That if in the end you are satisfied that the slate-writing is produced otherwise than by trickery, you shall abstain altogether from further proceedings against us, and suffer us to remain in England, if we choose to do so, unmolested by you.

"If, on the other hand, you are not satisfied, you shall be at liberty to proceed against us, after the expiration of one week from the conclusion of the six or more experiments, if we are still in England. You will observe that Slade is willing to go to you without witnesses of his own, and to trust entirely to your honour and good faith.

"Conscious of his own innocence, he has no malice against you for the past. He believes that you were very naturally deceived by appearances, which, to one who had not previously verified the phenomena under more satisfactory conditions, may well have seemed suspicious.

"Should we not hear from you within ten days from this date, Slade will conclude that you have declined his offer.

"I have the honour to be, sir, your obedient servant,

37, Spui-straat, The Hague, May 7th 1877.

"J. SIMMONS."

417

observed before him. The real educational value of Natural History, the development of the power of observation, will utterly escape those whose studies are confined to books.

The successive chapters of the work are devoted to a consideration of the cell as an individual; the cell as a member of a group of similar cells; the construction of the plant out of cells; the external form of plants; the life of the plant; special morphology and classification; the changes in the vegetation of the globe during past geological epochs; and botanical geography. The last division is illustrated with a map, showing the twentyfour regions into which the earth is divided by Griesbach in his "Végetation der Erde "- a classification which Mr. Bennett thinks "too unqualified," both with regard to the boundaries between the regions and the characters which distinguish them from one another. It is interesting to compare these regions with the geographical divisions of the animal world, as laid down by Mr. Wallace. We must own to a little surprise at finding Madagascar classed as an "Oceanic Island," along with the Azores, Madeiras, and Canaries.

The chapter on vegetable palæontology gives an accurate but necessarily very brief account of the flora of bygone ages.

In the section on the "Life of the Plant," the influence of temperature, light, &c., upon vegetation is carefully described.

The work is throughout abundantly illustrated, and will, we hope, prove useful to those real students who seek not to "pass," but to know.

The Geology of England and Wales. A Concise Account of the Lithological Characters, Leading Fossils, and Economic Products of the Rocks; with Notes on the Physical Features of the Country. By HORACE B. WOODWARD, F.G.S., of the Geological Survey of England and Wales. London: Longmans and Co.

MANY as have been the geological works recently put forth in England, there was still, we believe, room for a condensed work of reference on the geology of our own country that should be fully on a level with the present state of the science. This want Mr. Woodward has supplied in what we must pronounce a very satisfactory manner. His treatise is well arranged, comprehensive, accurate, and concise. All unnecessary verbiage has been carefully avoided, so that the student is not placed under the necessity of seeking out the facts he wants amidst a dreary waste of padding. Of speculation there is little. The author declares himself to be what is technically called a " uniformitarian," but he judiciously adds that "in concluding that the physical forces have been the same throughout geological time" we must guard VOL. VII. (N.S.)

against supposing their action to have been "always of similar intensity to that of which we have definite proof in the present." He also lays down a limitation which is sometimes conveniently overlooked by cavillers at geology and geologists. "The special province of the geologist," he reminds us, "is only to deal with the Earth after it was in a fit state to receive and support life, when the proportion of land to water was probably much as it is now, and the climate and physical conditions, though ever varying over the same area during the different geological ages, were subject to the same laws and attended by analogous phenomena. . . . To go back to the very earliest history of the Earth, when it was part of a nebulous mass, would be to trespass upon the region of the astronomer, and when we consider its latest history we come upon questions which must be answered by the geographer and the archæologist."

The author evidently accepts, in its general principles, the doctrine of Organic Evolution. He quotes, at any rate without formal disapproval, the opinion of Prof. Huxley, that "the less regard palæontologists pay to the deposit from which fossils are obtained so much the better, for not unfrequently has a new name been given to a known fossil because it has been found in strata where it was previously unknown." The same eminent author even longs for "a new race of paleontologists, utterly ignorant of geology "-a pious wish in which we find ourselves unable to join.

In treating of the economic bearings of geology, Mr. Woodward remarks that "the relation between health and geology is also a point which has in recent years received a good deal of attention, and maps have been published and memoirs written to show the relation between certain forms of disease and geological structure-even between geology and lunacy! It is well known, indeed, that a gravelly, sandy, or chalky soil is more healthy than a clay foundation, because the former are pervious to water and the latter is impervious. On the former there is less consumption than on the latter, as Mr. Whittaker and Dr. Buchanan have clearly demonstrated: the artificial removal of subsoil water has, however, done much to equalise the conditions. Again, the water-supply is a most important subject, for in some small country villages and towns the inhabitants suffer very much from its impurity. Situated, perhaps, on elevated ground, with a good porous soil, they yet suffer because of the disgraceful state of the drainage, the wells being shallow, and the sewage and even the churchyards draining into them. The cause of teetotalism will not find many admirers when it is often the women and children who suffer most from drinking impure water, while the men who take their beer are less subject to disease."

We fear that the sentence last quoted will bring down upon Mr. Woodward the gravest denunciations of the " temperance

419

party." But we cannot help remarking that it is in districts having a porous subsoil where polluted waters, and other evils arising from sanitary neglect, are most rampant. A stiff compact clay opposes an impassable barrier to the diffusion of cesspool and churchyard drainage. But over chalk and gravel, the cesspool and the well, though separated by an interval of perhaps a dozen yards, are practically identical. In a small town in Kent we even found that the sewage, after removal of the solids by means of subsidence-pits, was allowed to soak down and disappear in the permeable subsoil, which must thus become irredeemably saturated with putrescent matter, and must constantly give off noxious gases and vapours.

As regards the antiquity of the human species, the author admits that it appeared on the earth's stage unquestionably at a date very much earlier than our forefathers imagined. With Mr. Boyd Dawkins, he holds that man was co-existent, in this country and in Western Europe, with the lion, the hairy elephant, and the woolly rhinoceros, and that if his existence can be traced back to or even beyond the Glacial epoch, extending from 240,000 down to 80,000 years ago, a still higher antiquity must be assigned him.

The work is admirably illustrated, and is furnished with a good geological map of England and Wales, with a glossary of technical terms, a synopsis of the animal kingdom, a list of the principal works consulted, and a bibliography of the geology of the English counties.

We consider that Mr. Woodward's work merits almost unqualified commendation.

The Whitworth Measuring-Machine, including Descriptions of the Surface-Plates, Gauges, and other Measuring-Instruments, made by Sir Joseph Whitworth. By T. M. GOODEVE, M.A., and C. P. B. SHELLEY, C.E. London: Longmans and Co.

1877.

We all know how very superior English machinery is to that which is manufactured by many other countries, but we do not always recognise the great share which Sir Joseph Whitworth has had in perfecting the machinery whereby our most accurate work is done. The authors of the work before us state at the outset that "the two principal surfaces of essential importance in the workshop may be distinguished as a true plane' and a 'true cylinder.'" The nearest approach to the former is a surface of clean mercury at rest. Sir Joseph Whitworth has devoted much time and thought to the production of perfectly plane surfaces and accurate methods of minute measurement, and his instru

ments approach to accuracy as nearly as is possible. Messrs. Goodeve and Shelley have given an interesting account of the instruments, accompanied by good plates and woodcuts.

The Theory of Sound. By Lord RAYLEIGH, M.A., F.R.S., formerly Fellow of Trinity College, Cambridge. Vol. I. London: Macmillan and Co.

EVERY student of the mathematical theory of sound has felt the exceeding meagreness of the information on the subject within his reach. The ordinary text-books treat of Sound merely by way of an appendix to Dynamics and Hydro-dynamics, and consequently limit themselves to the most elementary parts of the theory, with scarcely a hint as to the existence of a mass of important recent investigations sufficiently numerous and valuable to require a separate treatment of the whole subject. The book before us is the first instalment of a work intended to remedy this deficiency, and certainly, so far as the range of this first volume extends, achieves a success.

After some valuable preliminary remarks on the ordinary theory of musical notes as due to vibrations, amongst which is to be found a remarkably clear exposé (p. 17) of the reasons for supposing the sensation of a simple tone to be due to a simple harmonic vibration, the author proceeds to describe various appliances for investigating the rapidity of the simple vibrations which may be present in any compound vibratory motion, illustrating at the same time the laws of superposition of small motions without interference, and showing very clearly the nature of the interference effect, in a simple case, of the superposition of motions which are so great that the squares and higher powers of the disturbance cannot be neglected an effect which shows itself in the production of vibrations whose periods are the doubles, sum, and difference of the periods of the originals. The application of the method of generalised co-ordinates to the problem of small vibrations about an equilibrium position is then discussed, and the main part of the work consists of the application of the results to the detailed examination of the vibrations of strings, bars, membranes, and plates. This discussion contains all that is most important in the work of recent investigators, amongst whom Lord Rayleigh holds a foremost place.

The theory of sound is perhaps somewhat uninteresting as yet to the general mathematical reader, but it is full of interest to the investigator on account of the facility and delicacy of the acoustical tests which can be applied to verify theoretical deductions, and the author has taken care to supply this element of interest in this work by constant exhibition of the results of a