60 T. H. Holland — Constitution of Later it e. 



has, of coarse, been frequently referred to as a product of solfataric 

 action, and the evidences have recently received exhaustive treatment 

 by H. Rosier, who, without referring to Bauer's work, doubts 

 Glinka's suggestion that kaolin and laterite are mere climatic facies 

 of weathering products.' 



The frequent occurrence of kaolin as an undoubted product of 

 what Judd defined as solfataric action,- and the absence of evidence 

 to show that it was formed by the action of subaerial agents, 

 naturally suggested that our laterites, generally spoken of as 

 ferruginous clays, should be more critically examined. Dr. Warth's 

 suggestion naturally occurred to me, and steps were taken to 

 investigate the chemical constitution of laterite ; but before any real 

 progress in the work had been made, Dr. Bauer's paper appeared, 

 and, as I think, practically settled the question. What is true of 

 the Seychelle laterite must, so far as one can judge, be true also 

 of the laterites in India which have not been sifted by running 

 water. To this point and a speculation I will return after briefly 

 summarizing Bauer's results. 



The following two analyses by Professor Busz are employed in 

 Bauer's discussion : — 



100-59 99-86 



No. I is a laterite capping granite, whilst No. 11 was found on, 

 and was presumably derived from, diorite on the Seychelle Islands. 

 Bauer says that the treatment of the first specimen with boiling 

 hydrochloric acid leaves about 50 per cent, of fine quartz-sand, 

 which can also be detected when the laterite is moulded between 

 the fingers. Similar treatment of No. II leaves a correspondingly 

 small residue of quartz. He, therefore, assumes that the silica is 

 present as quartz mechanically mixed with the other constituents ; 

 thus, by removing the silica, and calculating the results to 100, 

 we obtain : — 



100-00 



100-00 



In both of these cases the molecular ratio of Al, O3 : Hg 

 approaches that of gibbsite, AI2 O3 . 3 Hg ; but even without 

 considering the water united with the ferric oxide it is still deficient, 



1 Eosler, " Beitrage zur Kenntniss einiger KaoKnlagerstatten " : Neues Jahrb. fiir 

 Min., 1902, vol. xv, Beilage-Band, pp. 231-393. 



2 Judd: Quart. Journ. Geol. Soc, 1890, vol. xlvi, pp. 341-382. 



