lOO 



NATURE 



{Dec. I, 1887 



. . I never found one that exhibited a greater thickness 

 of coral limestone than 1 50 feet, or at the very outside 

 200 feet. . . . 



" The third inference is, that these upraised reef masses 

 in the majority of islands rest on a partially consolidated 

 deposit which possesses the characters of the ' volcanic 

 muds ' that were foimd, during the ' Chalhnger ' Ex- 

 pedition, to be at present for mitig around volcanic islands. 



" The fourth inference is, that this deposit envelops 

 anciently submerged volcanic peaks." 



Mr. Guppy states that his observations have made him 

 a strong adherent of the theory of formation of coral 

 islands advanced by Mr. Murray. 



These observations are indeed crucial between the 

 theories of subsidence and of solution, and point towards 

 the newer. The theory of subsidence demands that a coral 

 reef rising from deep water must be of enormous thick- 

 ness, and rest upon volcanic or fragmental rock ; that of 

 solution requires that the reef be of shght thickness and 

 rest on volcanic rock, or consohdated terrigenous mud, or 

 pelagic ooze. According to the former the reef grows 

 on the whole vertically ; according to the latter its main 

 extension is horizontal. Two of Darwin's principal 

 objections to the early conception of coral islands were 

 that it was absurd to suppose that submarine mountains 

 were numerous enough to provide foundations for all 

 the known reefs, and that it was impossible to imagine 

 sedimentation taking place at great distances from land. 

 The recent work of telegraph ships along the West Coast 

 of Africa and elsewhere has shown the extreme prob- 

 ability of submarine mountains existing in large numbers 

 throughout the ocean ; the cruise of the Challenger 'prowtd. 

 that the shells of pelagic organisms, wind-borne and 

 meteoric dust and volcanic ashes spread by ocean- 

 currents produce perceptible sedimentation in mid-ocean 

 at a rate varying in some inverse proportion to the 

 depth. 



Murray's theory can be brought readily to the test of 

 observation and experiment ; Darwin's cannot. It has 

 been shown in the laboratory that calcium carbonate is 

 soluble in sea-water, and is dissolved in greater amount in 

 water containing carbonic acid especially when under 

 pressure ; the decomposition of dead corals and the 

 respiration of living ones supply carbonic acid to aid in 

 the removal of their calcareous remains. If atolls are 

 formed in areas of elevation, they may ultimately be seen 

 and measured : if only in regions of subsidence, measure- 

 ment is impossible, and the vertical extent of the coral 

 limestone can only be guessed at. 



It must be confessed that the theory of solution in reef- 

 building has not yet been put before the world with any 

 approach to the completeness, lucidity, and grace with 

 which Darwin convinced and enchained the scientific 

 mind. The theory of subsidence is so beautiful, simple, 

 and satisfactory, that very strong evidence is required to 

 shake it ; but in the history of science men have more 

 than once been forced to say of a simple and satisfactory 

 doctrine — 



" 'Twas beautiful, 

 Yet but a dream, and so — Adieu to it ! " 



Neither Murray nor Guppy has proved the subsidence 

 theory to be a dream. Still, the solution theory has been 

 plainly set forth, and here we have facts which amount to 

 an absolute proof of its truth for one important group of 



coral islands. The proof is none the less convincing 

 because it is restricted in its application ; for it is concrete 

 and complete in itself, not abstract and cumulative like 

 the evidence for the subsidence theory. Mr. Guppy has 

 demonstrated that the old theory fails and the new suc- 

 ceeds in explaining the formation and structure of the 

 Solomon Islands, and coming at the present time this sup- 

 plies a powerful argument for the general applicability 

 of the solution theory — an argument that it will not be 

 easy to set aside. 



The book is short and interesting ; and, besides the im- 

 portant features we have alluded to, it contains much in- 

 formation about the islands visited, and the author's 

 adventures there. Hugh Robert Mill. 



AGRICULTURE IN SOME OF ITS RELATIONS 

 WITH CHEMISTRY. 



Agriculture in some of its Relations with Chemistry, 

 By F. H. Storer. Two Vols. (London : Sampson 

 Low, Marston, Searle, and Rivington, 1887.) 



THIS work, by the Professor of Agricultural Chemistry 

 at the Harvard University, is based on a course of 

 lectures delivered annually by the author. It is addressed 

 to students of agriculture and persons fond of rural 

 affairs, rather than to students of chemistry. Free 

 use has been made of German publications in 

 agricultural chemistry, and of the writings of Prof. S. 

 W. Johnson, of Newhaven, Connecticut. Some of the 

 matters treated of in his two well-known books, " How 

 Crops Grow " and " How Crops Feed," have been omitted, 

 or only lightly touched, in the present volumes, which 

 are therefore, to a certain extent, a supplement to those 

 books. 



The present volumes treat of the chemistry of the 

 atmosphere, of waters, of soils, and of manures, and of 

 their several relations to plants ; the chemistry of animal 

 life and nutrition is not dealt with. A large amount of 

 valuable information, partly of historical interest, has 

 been brought together ; and much of it is presented in 

 the somewhat old-fashioned English of the best writers 

 of New England. 



One illustration given by the author, to show that 

 liquids penetrate into plants through their roots, we do 

 not think very happy. He notes an observation made by 

 himself, that Indian corn made to sprout in a flower-pot 

 and watered with milk had white leaves ; and he suggests 

 that the minute particles of solid matter in the milk must 

 have entered the plant and caused the whiteness. He 

 admits, however, that the whiteness may have been due 

 to chemical action. In noticing the growth of plants in 

 artificial light, he hardly gives sufficient credit to the 

 observations of Siemens and of Deh^rain on growth in the 

 light of the electric arc, both uncovered and variously 

 shaded. Mr. Storer has scarcely that respect for earth- 

 worms with which Darwin has imbued us, for on the only 

 occasion he mentions them he styles them pernicious, 

 on the ground that harm is done to plants in pots 

 by their casts, which become slimy mud when watered, 

 and thus clog the pores of the earth and the roots of 

 the plants. 



In vol. i. p. 295, a serious mistake occurs, though 



