Reviews — Harrison's Mocks and Soils of Grenada. 419 



IV. — The Rocks a.nd Soils of Grenada and Carriacou and the 

 Agricultural Chemistry of Cacao. By J. B. Harrison, M.A., 

 F.G.S., Government Analyst of British Guiana. 60 pages. 

 (London : Waterlow & Sons.) 



ALTHOUGH, in the main, a treatise on agricultural chemistry, 

 this paper contains many facts of interest to the geologist. 

 The author states that the island of Grenada, the most southerly 

 of the Windward Group, "is purely volcanic in its origin, the 

 only signs of upheaval being raised limestone beaches towards 

 the extreme north." He regards it as being of more ancient date 

 than many other of the islands of the same group. The con- 

 figuration has been largely determined by denudation, and it is now 

 difficult to fis the exact sites of the ancient craters. The lavas 

 collected by the author during his comparatively short stay on the 

 island comprise hornblende-andesite, hornblende-augite-andesite, 

 augite-enstatite-andesite, augite-andesite with olivine and oliviue- 

 basalt. Full analyses of most of these rocks are given. 



The soils of the island have been derived either from the lavas 

 or from fragmental rocks of similar composition. Analyses of forty- 

 one examples of the Grenada soils are given, and suggestions are 

 made as to the methods by which many of these soils may be 

 improved. The author also discusses the relations between the 

 soils and the rocks from which they have been derived. He com- 

 pares the analyses of soils derived from hornblende-andesite and 

 from olivine-basalt (including olivine-bearing augite-andesite) with 

 the fuller analyses of the rocks, and draws conclusions as to the 

 relative proportions of the different constituents removed during 

 the process of soil-formation. He takes as the basis of his calcu- 

 lation the assumption that alumina is not removed ; and arrives at 

 the conclusion that in one case an increase of thirty per cent, of 

 iron-oxide has occurred. Now this may be almost said to be an 

 impossible result. It indicates, as the author himself suggests, 

 that alumina has been removed. A better result would probably 

 have been attained, by assuming that the total amount of iron-oxides 

 remained constant. As the point is an interesting one, let us take 

 the author's figures and recalculate on this basis. 



