discovery of some cause which could be reasonably regarded as not incommensurate with some of the effects ascribed to it. And, unlike the desperate though most laudable gropings of Lamarck, the simple solution furnished by Darwin was precisely what was required to give a locus standi to the evidence of descent.

But we should form a very inadequate estimate of the services rendered to science by Mr. Darwin if we were to stop here. The few general facts out of which the theory of evolution by natural selection is formed-viz. struggle for existence, survival of the fittest, and heredity —were all previously well-known facts; and we may not unreasonably feel astonished that so apparently obvious a combination of them as that which occurred to Mr. Darwin should have occurred to no one else, with the single exception of Mr. Wallace. The fact that it did not do so is most fortunate in two respects-first, because it gave Mr. Darwin the opportunity of pondering upon the subject ab initio, and next because it gave the world an opportunity of witnessing the disinterested unselfishness which has been so signally and so consistently displayed by both these English naturalists. But the greatness of Mr. Darwin as the reformer of biology is not to be estimated by the fact that he conceived the idea of natural selection; his claim to everlasting memory rests upon the many years of devoted labour whereby he tested this idea in all conceivable ways—amassing facts from every department of science, balancing evidence with the soundest judgment, shirking no difficulty, and at last astonishing the world as with a revelation by publishing the completed proof of evolution. Indeed, so colossal is Mr. Darwin's greatness in this respect, that we doubt whether there ever was a man so well fitted to undertake the work which he has so successfully accomplished. For this work required not merely vast and varied knowledge of many provinces of science, and the very exceptional powers of judgment which Mr. Darwin possessed, but also the patience to labour for many years at a great generalisation, the honest candour which rendered the author his own best critic, and last, though perhaps not least, the magnanimous simplicity of character which, in rising above all petty and personal feelings, delivered a thought-reversing doctrine to mankind, with as little disturbance as possible of the deeply-rooted sentiments of the age. In the chapter of accidents, therefore, it is a singularly fortunate coincidence that Mr. Darwin was the man to whom the idea of natural selection occurred; for although in a generation or two the truth of evolution might have become more and more forced upon the belief of science, and with it the acceptance of natural selection as an operating cause, in our own generation this could only have been accomplished in the way that it was accomplished; we required one such exceptional mind as that of Darwin to focus the facts, and to show the method.

It seems almost needless to turn from this aspect of our subject to enlarge upon the influence which a general acceptance of the theory of descent has had upon biology. We do not state the case too strongly when we say that this has been the influence which has created organisation out of confusion, brought the dry bones to life, and made all the previously dissociated facts of science stand up as an exceeding great army. Let any one turn to the eloquent prophecy with which the pages of the "Origin of Species"

terminate a prophecy which sets forth in order the transforming effect that the doctrine of evolution would in the future exert upon every department of biology—and he may rejoice to think that Mr. Darwin himself lived to see every word of that prophecy fulfilled. For where is now the "systematist . . . incessantly haunted by the shadowy doubt whether this or that form be a true species"? And has it not proved true that "the other and more general departments of natural history will rise greatly in interest that the terms used by naturalists, of affinity, relationship, community of type, paternity, morphology, adaptive characters, rudimentary and aborted organs, &c., will cease to be metaphorical, and will have a plain signification?" Do we not indeed begin to feel that 66 we no longer look at an organic being as a savage looks at a ship, as something wholly beyond his comprehension; and when we regard every production of nature as one which has had a long history, when we contemplate every complete structure and instinct as the summing up of many contrivances, each useful to the possessor, in the same way as any great mechanical invention is the summing up of the labour, the experience, the reason, and even the blunders of numerous workmen, when we thus view each organic being," may we not now all say with Darwin, "How far more interesting-I speak from experience-does the study of natural history become?" And may we not now all see that "a grand and almost untrodden field of inquiry on the laws of variation, or correlation, on the effects of use and disuse, on the direct action of external conditions" has been opened up; that our classifications, have become "as far as they can be made so, genealogies, and truly give what may be called a place of creation; that rules of classifying do "become simpler when we have a definite object in view;" and that "aberrant species, which may fancifully be called living fossils," actually are of service in supplying "a picture of ancient forms of life?" And again, must we not agree that "when we can feel assured that all the individuals of the same species and all the closely-allied species of most genera, have, within a not very remote period, descended from one parent, and have migrated from some one birth-place; and when we better know the many means of migration, then, by the light which geology now throws, and will continue to throw, on former changes of climate and of the level of the land, we shall surely be able to trace in an admirable manner the former migrations of the inhabitants of the whole world?" And who is now able to question that "by comparing the differences between the inhabitants of the sea on the opposite sides of a continent, and of the various inhabitants on that continent in relation to their apparent means of migration, some light can be thrown on ancient geography?" Or, if we turn to "the noble science of geology," do we not see that we are beginning "to gauge with some security the duration of intervals by a comparison of the preceding and succeeding forms of life?" And last, though not least, have we not found this one short sentence so charged with meaning that a new and extensive science, second in importance to none, may be almost said to have grown out of what it states :-" Embryology will often reveal to us the structure, in some degree obscured, of the prototypes?""

If the progress of science during the last two-and

twenty years has in so astonishing a measure verified the prophecy of the "Origin of Species," surely, in conclusion, we are more than ever constrained to agree with the sentiments expressed by its closing words :-"When I view all beings, not as special creations, but as the lineal descendants of some few beings which lived long before the first bed of the Cambrian system was deposited, they seem to me to become ennobled. . . . There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved."

THE

(To be continued.)

ECLIPSE NOTES1

III.

HE eclipse of 1882 is now over, and it is not too much to say that the observations have been most successful. Much more work has apparently been done in former eclipses, but it has been of a far more general nature, and, as the old saw has it, dolus latet in generalibus. This year the work has put on very much more of a quantitative look, and each observation therefore more or less means a real step in advance. And indeed the time had come when this should be so, for day by day the quantity of laboratory work done which can be more or less compared with eclipse observations is increasing, and in the case of general observations either in one case or the other comparisons are impossible. I have taken many prior occasions of insisting upon this point; but perhaps the reason why this principle has been so generally acted upon on the present occasion has been a capital example set to future eclipse parties. Some days before the eclipse there was a regular Congress of the leaders of the different expeditions and the chief observers, held under the presidency of Mahmoud Pacha, the astronomer at Cairo, and not only was the general plan of observations agreed upon but the necessity of a limited field of inquiry was generally acknowledged; hence at the moment of the eclipse each worker had only a limited part of the spectrum to study, and the instrument to be employed whatever its form, and there were many forms employed, was carefully prepared for this part, and this part only, before totality.

In the way of dispersion, MM. Thollon and Trépied outdistanced all their confrères, as each had the most powerful form of Thollon spectroscope yet constructed. The dispersion in this instrument is about the same as that given by a Rutherfurd grating (of 17,000 lines to the inch) in the third order, with this important difference, that the quantity of light is much greater, so that a spectrum can be much better observed. With these spectroscopes, object-glasses of 9 inches aperture, and siderostats of a simple altazimuth focus were employed. All the other spectroscopic arrangements, whether for eye or photography, were mounted on equatorial stands. The instruments employed for exposing the rapid plates, which recent progress in photographic science has placed in the hands of the astronomers, were perhaps the most complicated Thus we had a camera with large lens some 5 feet focus; on this a slitless spectroscope of the Fraunhofer I Continued from p. 52.

form, similar to that employed in Siam in 1875, but with a prism of greater angle in front of the object-glass then a tele-spectroscopic camera of small dispersion with small image of the sun in the slit, and last of all an ordinary camera of small focus.

Perhaps before I go further it will be convenient to give a collective note agreed upon in a second congress held two hours after the eclipse. This will show the general opinion as to the general results.

"Unprecedented facilities afforded by Egyptian Government for observation of the eclipse. The plan carried out was agreed upon by the members of the English, French, and Italian expeditions. The accord among the results is very satisfactory. Photographs of the corona and of its complete spectrum were obtained by Schuster on Abney's plates, H and K being the most intense lines. A study of the red end of the spectrum of the corona and prominences was made by Tacchini. A comet which was very near the sun, and a very striking object, was photographed and observed with the naked eye. Bright lines were observed before and after totality of different heights by Lockyer, and with intensities differing from the Fraunmination of the place of the coronal line at 1474, of hofer lines by Lockyer and Trépied. An absolute deterKirchhoff's scale, was made by Thollon and Trépied. The absence of dark lines in the corona spectrum was noted by Tacchini and Thollon with very different dispersions. Many bright lines in the violet were observed in the spectrum of corona by Thollon, and were photographed by Schuster. Hydrogen and coronal lines studied in grating spectroscope by Puiseux, and in direct-vision prism by Thollon. Rings observed with grating by Lockyer, first, second and third orders. Continuous spectrum relatively fainter than in 1878, and stronger than in 1871. Intensification of absorption observed in group A at the edge of the moon by Trépied and Thollon.

66

LOCKYER, TACCHINI, THOLLON.” Having given the collective note, I may be permitted to refer first to those observations which specially bear upon the matter dwelt upon in these notes-observations touching the bright lines seen before and at the moment of totality.

The importance of this part of the work arises from the following considerations :-If there be a layer of a certain height, by the absorption of which the lines of Fraunhofer are reversed, the lines visible under the stated conditions during eclipses will all be of the same height, and their intensities will all be those of the Fraunhofer lines; if, on the contrary, the reversing layer is a myth, as I believe it to be from a consideration of all the prominence and spot work done up to the present time, the lines will not be all of the same height, and the intensities will widely differ from those of the general spectrum of the sun, for the following reasons:—

As explained in my first batch of notes, it is most probable that the solar spectrum is built up of the absorption of different layers, and not of one, thus

A, B, C, layers.

A, layer nearest the sun, and therefore hottest, and

roots of plants, it is necessarily greater in wet seasons such as have been the rule for the last few years.

We believe that Pasteur was the first to suggest, twenty years ago, that the process of nitrification going on in soils and waters might be due to the agency of an organism; but it was not until the last five years that the researches of Schlösing and Müntz and of Warington conclusively showed that this is the case and that the organism is a bacterium. This bacterium is present in all fertile service soils and under the proper conditions of temperature, moisture, supply of oxygen, and presence of salifiable base is continually converting ammonia and nitrogenous organic matter, which has passed the putrefactive stage, into nitrates. That nitrates are the chief form from which most crops and especially the cereals assimilate their nitrogen is now admitted generally, even by the few physiologists who still cling to the belief that plants can assimilate free atmospheric nitrogen; the very great use of this nitrifying organism is thus apparent. It may be remarked in passing that this Schizomycete is able to effect a change in a mineral substance, a nmonia, causing its oxidation into nitric acid, all other known organised ferments being concerned in the transformation of organic bodies, and this is an operation hitherto unsuspected in the life of any Bacteria.

Nitrification takes place in soils most rapidly in the hot months of the year, and as a cereal crop assimilates little or no nitrogen after June, but merely transfers that already taken up and present in the roots, stems and leaves to other organs, it follows that, on a cornfield, in the late summer and the autumn months, nitrates will be formed and, will, in the event of wet weather, be readily washed out of the soil.

1

Observations made during many years at Rothamsted, and recently published by Messrs. Lawes, Gilbert, and Warington, show the extent to which this loss of nitrates may occur. They find that on land uncropped and unmanured, that is, a bare fallow, during 4 years 1878-1881, nearly forty-two pounds of ritrogen per acre per annum, equal to nearly two and a half hundredweight of ordinary nitrate of soda, was lost by drainage. They also estimate that on land under continuous wheat cropping from ten to twelve pounds of nitrogen per acre per annum was lost by drainage from plots which received no nitrogenous manure. When nitrogen is applied in the manure, con siderably larger quantities are lost in the drainage, and this is exclusive of that diffused into the lower layers of soil below the reach of plant roots, and of that which may under certain conditions be lost by deduction to elementary nitrogen.

In an ordinary rotation the loss of nitrogen will be considerably less than in these experiments, for crops will often be growing for months after the cereal crop is

removed, and thus conserve the available nitrogen and store it up for future use. It is however obvious, that, with a bare fallow favouring the production of nitrate, followed by a wet season, a very considerable loss of available nitrogen will occur through loss of nitrates, and it becomes a matter for the farmer to consider whether it is to his advantage, for the sake of cleaning his land, to take the risk of this loss and supply the nitrogen at a

Journal of the Royal Agricultural Society [2] xvii. an! xviii. ; and Journal of Society of Arts, April 7th, 1882.

cost, in ammonia, salts, or Chili saltpetre, of nearly a shilling per pound, or on the other hand, adopt some system of cultivation and cropping by which much of the loss may be obviated. On some soils the growth of an autumn green crop would save most of the nitrates and leave the land in fair condition for a succeeding crop ; naturally the decision as to the advisability of such a course must rest in each case with the individual farmer.

The Agricultural mind appears to always require a panacea from the scientific man before it will accept his results as of any use. At a recent meeting of the Farmers' Club it was observed by a leading agriculturist, that, although Mr. Lawes (now Sir J. B. Lawes) had discovered the way in which nitrogen was lost, he had not told the farmer how to retain the goods effects of nitrogenous manures in adverse seasons. The discovery of the manner in which the loss occurs is, however, an immense step in the right direction, and moreover Lawes and his colleagues have clearly shown that with a growing crop on the land the loss is very greatly lessened.

This bacterium of nitrification is but one of a great number of the lower forms of life now engaging the attention of scientific men, which are, or ought to be, of immense interest to the scientific pursuit of agriculture. The researches of Pasteur on the life history of Bacillus of Anthrax, Aitken and Hamilton's investigations now being conducted into the causes producing braxy and louping ill; and the study of the organisms concerned in the changes which occur during the souring of milk and the ripening of cheese are kindred studies bearing in a direct manner on the daily practice of the farmer. Of no less interest too is the biological work done by Kühn and Liebscher, which has traced the beet sickness to the presence of a Nematode, while the investigations into the life history of Hemileia vastatrix, the too well-known coffee leaf disease, the Plasmidiophora, which is the proximate cause of anbury in turnips, and the fungus of potatoe disease, all point to the growing relation between the kindred sciences of biology and agriculture. Illustrations might be multiplied almost indefinitely but these are of sufficient importance to show that the work of the microscopist and biologist has a wide and deep influence, first of all on the practice of agriculture, and through it on the comforts and the pockets of the consumers at large.

THE TRANSIT OF VENUS, 1874 Account of Observations of the Transit of Venus, 1874, December 8, made under the Authority of the British Government. Edited by Sir George Biddell Airy, K.C.B., Astronomer-Royal.

THIS volume, recently published under the authority

of the Treasury, contains the official account of observations of the last transit of Venus, by the five expeditions organised at the public expense and the reduction of the observations.

In an Introduction Sir George Airy briefly recapitulates the various steps taken by himself with the view to the efficient observation of this phenomenon, from his first communication to the Royal Astronomical Society in April, 1857, "On the means which will be available for correcting the measure of the sun's distance in the next