determinations of nine southern stars by Gill and Elkin, in 1882-3, showed the heliometer to be the instrument best adapted for this class of work. They fixed the distance of a Centauri-still our nearest known sidereal neighbour-at twenty-five billions of miles; showed Sirius to be about twice as remote; and the brilliant Canopus to lie altogether beyond the reach of their soundings. Dr. Gill succeeded Mr. Stone as

H.M. Astronomer at the Cape in 1879, Mr. Stone having occupied the post from the retirement of Sir Thomas Maclear in 1870. At Greenwich the administration was transferred, in 1881, from Sir George Airy to Mr. W. H. M. Christie.

Problem.

A profound alteration has, since 1846, affected ideas re- The garding the structure of the universe. Sir John Herschel's Nebular description of the Magellanic Clouds as aggregations of sidereal matter in all stages of condensation proved, as Whewell insisted in 1853, and Herbert Spencer in 1858, that star-clusters and nebulæ differ generically; and the fact was rendered patent by Huggins's application to them of the spectroscope. The distribution of nebula, too, in obvious correspondence with the

T. G.
BONNEY.
Geology

ontology, 1846-1885.

lines of the Milky Way (shown in Mr. Sidney Waters's chart of 1869), effectually reduces them from the status of independent starry realms to the less pretentious rank of members of the galactic system. This truth was enforced in many of R. H. Proctor's writings. Thus, the investigation of the nature, distance, and architecture of the Milky Way has come to be the prime object of cosmical inquirers.

USING 1833, the year when the publication of Lyell's" Principles " was completed, as a new point of departure, we may trace the and Palæ progress of the science down to the present day. Soon after this date a separation into subordinate branches becomes more easily recognised. The palæontologist found an ample field in studying fossils, not only as the stratigraphist had already done, for chronological purposes, but also for the significance of their zoological (or botanical) affinities and diversities. In this matter, during the earlier part of the century, Brongniart, Deshayes, and Lamarck, in France, were ahead of any English workers in their knowledge of fossil conchology, and Cuvier may justly claim to be the father of vertebrate palæontology. But soon after his death (in 1832) Richard Owen began to rise into repute as a British successor to the distinguished Frenchman, and a little later-early in the fourth decade-Edward Forbes became distinguished for work among the invertebrates, which was ended by his death, while still in his prime, in 1854.

Palæontology

In 1847 the Palæontographical Society was established, with the avowed intention of figuring all the British fossils. Among the contributors to the splendid volumes which are annually issued will be found most of the paleontologists who have attained eminence in Britain. It must suffice to name only a few memoirs from those members whose work is done, such as that of T. Davidson, on the Brachiopods; J. W. Salter, on the Trilobites; Milne Edwards, Haime, and P. M. Duncan, on the Corals; T. Wright, on the Sea-urchins and Starfish; Searles Wood (aided by his son), on the Crag Mollusca; and R. Owen, on extinct Reptiles and Turtles. The work also of W. B. Carpenter, on the Foraminifers; of his son, P. H. Carpenter, on the Crinoids; of Hugh Falconer and T. H. Huxley, the one in certain, the other in many departments of vertebrate palæonto

Natural
Selection

and the

Record.

logy, and that of W. C. Williamson, in fossil botany, though published elsewhere, must not be forgotten. Many still living have followed in their steps, but an enumeration of these, in the limits to which this notice must be restricted, would be a mere catalogue of names; a selection would be an invidious task.

In 1859 Charles Darwin published his famous book “On the Origin of Species by Means of Natural Selection" (p. 434). This Geological idea, which had occurred independently to A. R. Wallace while he was at work in the Malayan Archipelago, though mainly an induction from the study of living animals and plants, obviously depended also on the evidence of fossil forms. At first sight this seemed, on the whole, unfavourable, and the independence of species was maintained by not a few eminent palæontologists, although Darwin in his famous chapter on "the imperfection of the geological record" had indicated the need of caution in dealing with negative evidence. But evolution, as the new doctrine was called, found from the first an advocate in T. H. Huxley; and more recent discoveries in paleontology have not only removed many difficulties, but also supplied much additional evidence, so that the old idea of separate centres of creation now finds but few supporters among philosophic naturalists.

The

Glacial

Theory.

One immediate result of the publication of the "Principles was to give greater prominence to the study of physical geology, a subject hardly separable from physical geography. The older geologists had seen in mountain-peaks and valleys the records of mighty movements of the earth's crust, and W. Hopkins, of Cambridge, had attempted to explain the valleys of the Weald

a result of strains in the upheaval of the region; but as "convulsionist" views lost ground, a more and more confident appeal was made to the forces still at work. The credit of indicating clearly that the rivers make the valleys, rather than the valleys the rivers, is due, more than to any other man, to J. B. Jukes, Director of the Geological Survey in Ireland. His views were published about the year 1862, and are now generally accepted among geologists.

But before this another great forward step was made. In many parts not only of Britain but also of Northern Europe superficial deposits of gravel, often coarse as well as fine, of sand and of clay, commonly full of stones, occur at various elevations,

lying like a mantle over the ordinary Tertiary and older rocks. Some of these stones attain a large size, and isolated boulders are scattered here and there over the country. These were formerly claimed as proofs of the tumultuous action of an universal deluge, but careful study began to show the difficulties in this hypothesis, and appeal before long was made to another means of transport. About

1835 De Charpentier, a Swiss geologist, maintained that the erratics and boulder clays of his country had been deposited by glaciers at a time when they had extended far beyond their present limits in the Alps; and in 1840 Agassiz, of Neuchâtel, devoted himself to a careful study of the Alpine glaciers. He was visited, while thus occupied, by J. D. Forbes, noted for his researches into the physics of glacier ice, and by W. Buckland, with whom he afterwards investigated the north of Britain. Here they found signs of ice action similar to those in Switzerland; the discovery, announced by Buckland, though too startling to be at once accepted, gradually obtained credit, and further examination showed that all the mountainous districts of Britain had been similarly occupied by glaciers. But as to the extent of the ice considerable difference of opinion still prevails. By one school a very large part of the English lowlands, the bed of the Irish Sea and most of Ireland as well as Northern Europe to the south of Berlin, are asserted to have been enveloped in a great ice sheet, which is even believed by some to have invaded the country from Polar regions. Another school restricts the ice within narrower limits, and attributes most of the lowland deposits, with certain shell-bearing gravels found even in the hill regions, to the action of shore-ice and floating ice while the land was submerged.