Maryland Geological Survey 119 



portion by this method is indicated by the work of Mohr, 1 who carries 

 his settling to periods of several weeks. But he too separates between arbi- 

 trary limits and his curve is therefore not continuous. Moreover, his 

 results show that in the very finest portions some further differentiation 

 could probably be made. 



To go into a more detailed discussion of methods other than the 

 mechanical for the differentiation of the constituents of argillaceous sedi- 

 ments would not be in place here. Reviews and discussions of such 

 methods can be found in a paper by Stremme and Aarnio, " Die Bestim- 

 mung der anorganischen Kolloide," etc., Zt. f. prakt. Geol., vol. xix, 1911, 

 pp. 329-335, and van der Leeden und Schneider, " Ueber neuere Methoden 

 der Bodenanalyse u. der Bestimm. der Kolloidstoffe im Boden," Int. Mitt, 

 f. Bodenkunde, vol. ii, 1912, pp. 81-109, in which, among others, the 

 method of Mitscherlich referred to above is discussed. There may also be 

 much to be learned about the colloidal matter by the method of staining 

 and microscopic study in which a beginning has been made by Hundes- 

 hagen. 2 But it may be said in conclusion that the analysis of clay-bearing 

 sediments on a scientific basis, that is, on the basis of their natural con- 

 stituents, has not yet been attained. 



To continue the description of the method of analysis that has been 

 employed in the present study, the clay suspension in the funnel was 

 tapped into a large evaporating dish. Thoulet, who, working with fresh 

 modern sediments, was not obliged to add ammonia to disintegrate, then 

 added a few drops of alum solution to precipitate the clay, settled, siphoned 

 off as much of the supernatant water as possible, and evaporated to dryness 

 over a gentle heat. As ammonia was used in most of the present analyses, 

 it had to be neutralized, which was done with hydrochloric acid. Per- 

 formed at first approximately, this neutralization produced irregular 

 results due doubtless to solution with an excess of acid, while to neutralize 

 exactly was very tedious. Moreover, experiment with one sample showed 



1 Mohr, E. C. Jul., Mechanische Bodenanalyse. Bull. Dept. de l'Agr. aux Indes 



Neerlandaises No. 41, Buitenzorg, 1910, 33 pp. Ergebnisse mech. Analysen 



tropischer Boden. Ibid: No. 47, 1911, 73 pp. 



2 Hundeshagen, Ueber die Anvendung organischer Farbstoffe zur diagnosti- 

 schen Paerbung mineralischer Substrate. Neues Jahrb. f. Min. etc. Beilage-Bd. 

 xxviii, 1909, pp. 335-378. 



