J. R. Kilroe — Later ite and Bauxite in Germany. 541 



The sulphuric acid brought up with C Oo in springs, as that at 

 Carlsbad,' could only be effective very locally, and, when we turn to 

 the consideration of sulphurous acid vapours, we cannot overlook the 

 following points, viz. : — 



1. The deleterious, if not death-dealing, effect of such vapours on 

 vegetation ; workable seams of lignite sometimes exist side by side 

 in the same zone, and of contemporary formation, with a rich seam 

 of iron-ore over a deep and wide-spreading lithomarge. 



2. Nothing is more striking than the even way in which solution 

 and deposition of Aln Og, as hydrate, must have balanced each other in 

 the aluminous layers of rothen Hang. Solution and deposition must 

 have been all but simultaneous ; more correctly, perhaps, they rapidly 

 alternated. In following the process, if we regard the solvent as 

 Hg S O4, and the precipitant Ca C O3 in solution, then, although Alo O3 

 could have been precipitated freely by Ca C O3 in lake waters, as is 

 suggested by Coquand for the occurrence of bauxite in Bouches du 

 Ehone, it is extremely difficult to imagine how rapid alternations of 

 the process could have gone on in close, deep rock interstices where 

 we assume ordinary percolation and capillary action. Por when 

 Al3Ko(S04)j^ in solution below, meets Ca C O3 in solution, descending, 

 the interstices would become choked with precipitated Ca S O4 and 

 Alg O3 3 Hg to impede, if not entirely hinder, both percolation and 

 capillarity. 



Strong acids were no doubt engaged in the processes, chiefly in the 

 initial stages, after which the chief solvent would have been C O3. 

 Maclaren maintains that " energetic chemical action in the presence 

 of abundant carbon dioxide" effected complete decomposition in the 

 conditions under which Indian laterites were formed. It is hazardous 

 to propose definite formulae in attempting to represent what probably 

 takes place, where reactions must obviously be so complex. Many 

 processes are probably at work, simultaneously; and it is very doubtful 

 if the simple formulae proposed by Maclaren,^ or that by Van Hise 

 quoted by the Editor of the Geological Magazine, for the sericitization 

 of felspars, or any representing transformations through zeolites ^ or 

 substances allied to them, could — however tempting such formulae 

 might appear — present all that takes place, or even the main line 

 of reactions along which alteration would run. Keeping in mind the 

 chief desiderata, viz., the detachment and bearing away, in soluble 

 form, of silica in some proportion from the silicates ; also the detach- 

 ment of alumina, and its retention in a nicely balanced condition — 

 now in solution, now precipitated as hydrate — the following general 

 formulae representing mass-action would seem to include the principal 

 stages in the process of transformation. Let E'3 be the alkalies ; R"o 

 the alkaline earths and ferrous oxide; and Eg 63 the alumina and ferric 

 oxide ; also let a compound silicate be affected in the first instance by 

 HoSO^; then <?(R'oO), J(R"0), c (Ro O3), ^^(SiOg) ^- ?^ Kg SO^:^ 

 .» E'g S O4 + y R" S" O4 + 2 R'g Rg (S 64)4 \ X, whcrc X represents 



1 Watts' Chem. Diet., vol. v, p. 1017. 



2 Geol. Mag., 1906, pp. 539-40. 



2 I have found eompact basalts as highly transformed as were those which had 

 been manifestly zeolitie, and under similar circumstances. 



