536 Malcolm Maclaren — lite Origin of certain Laterites. 



Here, then, it seems to me we have a case in point, aflbnling good 

 evidence of an interglaoial period with abundance of heat, and yet 

 not enough to cause a decided reversal of climate, but onl}' sufficient 

 to clear out the heavy mass of ice which filled (he basin of the 

 Moray Firth. Such a result certainly could not have been 

 accomplished without (he expenditure of an enormous amount of 

 heat, which in districts where there was no ice to dispel would have 

 produced a decidedly warm climate. During the thawing of the ice 

 and its reduction into ice-cold water the air would remain cold, and 

 not until the ice had completely disajipeared would the climate 

 become genial. Before this could happen in the Nordiern di8tric(s 

 the interglacial spell of warmth might be passing away, and hence 

 no genial climate would result. 

 Ellon, Ahuiuieexshiuk. 



III. — On tiik Origin of ckktain Lateuitks. 

 By Malcolm Maclaken, B.Sc, F.G.S. 

 rnHE various views put forth prior to 1893 to account for the 

 X origin of Indian laterites have been clearly and sufficiently 

 discussed in Oldham's edition of Medlicott & lilanford's Manual 

 of the Geology of India (pp. 369 et seq.). Since that year the 

 only contribution of importance to the literature of lateritic genesis 

 in India is a paper by IMr. Thos. H. Holland, F.K.S., the present 

 Director of the Indian Geological Survey,' having f()r its text 

 the conclusions of Bauer.- In it the author suggested that laterite 

 might owe its origin to ''some lowly organism," but no sufficient 

 data were advanced in support of the suggestion. Bauer's specimens 

 indicated a certain amount of dehydration in laterites. and this 

 fact, together with the absence of hydration products from certain 

 peridotites in Southern India, ^ was deemed to indicate a general 

 dehydration for the bauxitic laterites of the Deccan. The gibbsite 

 (Alo O3, 3 H^ 0) of laterite was supposed to be dehydrated to diaspore 

 (AloO;., H., 0), and it was assumed that "this irregular loss of 

 water is probably the cause of variation in bauxite." * 



To account for the energ}' necessary for dehydration the ingenious 

 theory of the possible superiority of " crystalline affinity " over 

 " chemical affinity " was developed (loc. cit.. p. G9). and the con- 

 clusion was drawn that " limonite and gibbsite must be regarded as 

 unstable at tropical temperatures."* 



Of late years valuable analytical researches on the constitution of 

 laterite have been made by Dr. Warth,^ who may justly be considered 



> Geol. Mao., Doo. IV, Vol. X (1903). pp. TiO-GO. 



' " Beitn'igo zur Goologie der Sevchelleu " : Neues J;ihr. fiir Afiu., vol. ii (1898), 

 p. 163. 



3 Geol. Mao.. Deo. IV, Vol. VI (1899), pp. 31, ;H2. 



* lb.. Dec. IV. Vol. X (1903), p. (>;>. 



» See, however, Geol. M.\o.. Dec. IV, Vol. X (1903), p. 139. 



« Mill. Mao-., vol. xiii (1902), p. 172. Geol. M.vo., Dec. IV, Vol. X (1903), 

 p. l.H ; ib., t)ec. V, Vol. II (1905), p. 21. 



