June 24, 1909J 



NA TURE 



487 



course southward was taken, until a latitude of 64° 

 was reached ; from that point the line talven was by 

 Kerguelen Island to Sumatra, and thence by Ceylon 

 and the East African coast to the Suez Canal. This 

 route was sufficiently different from that of the 

 Challenger and other exploring expeditions to supply 

 much new and important evidence, in the 217 sound- 

 ings and dredgings, concerning the contours of the 

 floors of the Atlantic and Indian Oceans, and the 

 deposits that cover them. 



The nature of the materials brought up at various 

 points during the voyage is well illustrated by a 

 series of fine plates, similar to those accompanying 

 the Challenger volumes. The globigerina ooze from 

 different latitudes in the two oceans is represented by 

 four very beautiful figures; the pteropod, radiolarian, 

 and diatomaceous oozes, with the glauconite and 

 coprolitic muds, have eight excellent figures devoted 

 to them. Interesting points of difference from the 

 deposits figured in the Challenger volume may be 

 noticed on a careful comparison, though the general 

 features are the same. 



Of greater interest, however, than the organic 

 defxjsits are the components of these oozes which are 

 of mineral origin. No trace was found of any 

 particles to which an extra-terrestrial origin could 

 be assigned, neither particles of nickel-iron nor 

 chondritic fragments occurring. A discussion is 

 given of the mode of transport of the mineral frag- 

 ments — by ice, wind, volcanic eruptions, and currents 

 — and of the alternation of these deposits as proved by 

 the soundings. In addition to the accounts of the 

 glauconite, phillipsite, palagonite, and manganese 

 nodules, of which some interesting particulars are 

 given, we have in this monograph much valuable 

 information concerning materials occurring at the 

 bottom of ^he deep oceans, previously very imperfectly 

 described or not known at all. 



Besides the nodules containing up to 36 per cent, 

 of calcium phosphate from the Agulhas Bank, a blue 

 coprolitic mud is described from near the mouth of 

 the Congo, at a depth of 214 metres, which contain 

 numerous small, oval, phosphatic masses, believed 

 by Sir John Murray to be the excrement of echino- 

 derms. Among the concretions from the Agulhas 

 Bank were found nodules containing 33 per cent, of 

 calcium carbonate, 28 of calcium phosphate, 14.6 of 

 calcium sulphate, and 4-8 of magnesium carbonate, 

 with some ferric oxide, alumina, and silica. These 

 nodules w-ere dredged at a dej)th of 155 metres. 



Perhaps the most interesting and suggestive, cer- 

 tainly the most novel, portion of this memoir is that 

 which deals with the exploration of the " Seine 

 Bank," a portion of the sea-bottom lying north-east of 

 Madeira, which rises with steep slopes from depths of 

 more than 4000 metres to within 146 metres of the sur- 

 face of the ocean. This bank was first discovered in 

 18S2 and 1883 by the cable steamers Seine and Dacia. 



The calcareous sand dredged from the bank in 

 question, at a depth of 150 metres, was found to be 

 made up of fragments of Bryozoa, corals, and 

 hydroid polyps, and shells and pteropods and other 

 moUusca, spines, and plates of echinoderms, various 

 Foraminifera, spicules of alcyonarians and sponges 

 NO. 2069, VOL. 80] 



with fragments of crustaceans and otolites of fish. 

 The inorganic constituents consisted of fragments of 

 pumice and felspar. 



The chemical analysis of different samples of this 

 calcareous sand by Herr Pillow, of Berlin, revealed 

 the interesting fact that the material had undergone a 

 greater or less amount of dolomitisation. The several 

 analyses gave percentages of ii'ii, i4'j6, 17^28, and 

 i8'i7 of magnesium carbonate, with a small amount, 

 in some cases, of calcium phosphate. The study of 

 thin sections of the material, stained by Lemberg's 

 solution, showed that the dolomitisation was most 

 marked in the calcareous mud, in which the frag- 

 ments of organisms were embedded, but had also 

 commenced in the latter themselves. Sometimes as 

 much as nine-tenths of the cementing matrix of the 

 deposit was found to be converted into the character- 

 istic rhombohedra of dolomite. 



The similarity of these results with those obtained 

 by the study of the materials sent home by the 

 Funafuti expeditions is very striking. The proportion 

 of magnesium carbonate in the Seine-Bank material 

 does not greatly exceed what is found in many or- 

 ganic deposits in which a gradual leaching out of 

 the calcium carbonate appears to have taken place. 

 It is interesting to notice that the depth of the deposits 

 of the " Seine Bank " is only about 500 feet, and at 

 this depth the chemical changes in question may be 

 assumed to have taken place. The conditions under 

 which the dolomitisation of limestones is brought 

 about are still very obscure, but the facts described 

 in the present memoir, with those contributed by 

 Hogbom, Natterer, Nichols, and other observers, are 

 valuable contributions towards the solution of the 

 problem. 



Another interesting discovery was made in the 

 South Atlantic Ocean in soundings, where the globi- 

 gerina ooze was found to graduate into the red clay 

 at a depth of 5040 metres. In the mixture of clay 

 and calcareous ooze there were found numbers of 

 minute, clear yellow crystals, which were shown by 

 Prof. Linck to be the fundamental rhombohedra of 

 calcite without any trace of magnesium carbonate. 

 We seem to have evidence here that, at depths at 

 which solution of calcareous organisms is going on, 

 the dissolved matter may, under certain conditions, be 

 re-deposited as calcite. 



The whole of the memoir before us, indeed, abounds 

 with facts and suggestions that cannot fail to be of 

 great service in the solution of the problem of the 

 chemical operations going on at various depths in the 

 ocean — a problem which as deeply interests the geolo- 

 gist as it does the geo-physicist. J. W. J. 



THE GEOLOGICAL SOCIEIY OF GLASGOW. 

 History of the Geological Society of Glasgow, 1858- 



igo8, with Biographical Notices of Prominent 



Members. Edited by P. Macnair and F. Mort. 



Pp. v + 303. (Glasgow: Published by the Society, 



1908.) Price 6s. net. 



THE city of Glasgow, situated in the midst of a 

 busy coal- and iron-mining district, within easy 

 reach of the Highlands, the Western Isles, and the 

 Southern Uplands, all replete with fascinating and 



