THE NATURAL HISTORY OF MARL SOI 



distilled water was not clear when the experiment terminated, 

 but was nearly so, showing that the subsidence was not quite so 

 rapid in distilled water as in natural lake or river water. 



These results indicate that, if for any cause the marl in a 

 marr lake is stirred up effectually, as it may be in those where 

 the beds are exposed to wave action, the water will remain 

 turbid for some time; even in summer time the chances are that 

 there will be sufficiently frequent high winds to keep the water 

 always turbid. It may be stated that in some of the lakes which 

 have been studied by the writer, the marl beds have filled the 

 entire lake to within a fraction of a meter of the surface of the 

 water, with some parts only a few centimeters deep. Until such 

 shallows are occupied by vegetation the water is likely to be 

 turbid from the mechanical action of waves upon the deposits. 

 At Littlefield Lake, described elsewhere,^ the water is only slightly 

 turbid, although there are extensive shallows and exposed banks, 

 but there the body of water is extensive and of considerable 

 depth, while the greater part of the exposed marl is granular 

 and the particles too coarse to be held long in suspension, and 

 the finer deposits too small and too well protected to be reached 

 by effective waves, so that the amount of suspended marl is not 

 great enough to produce marked turbidity in the entire body of 

 water. 



It may be worthy of note that the residue of suspended 

 matter, filtered out from the sample of Chara fragments (analy- 

 sis (4) above) was sufficiently fine to give a marked turbidity 

 to distilled water for several days, and at the time of filtering 

 had not subsided, demonstrating the fact that very finely divided 

 particles may originate from the simple breaking up of the 

 Chara plants by ordinary decomposition of the vegetable matter. 



It is difficult to account for the fact that the deeper parts of 

 marl lakes are generally free from any thick deposits of a cal- 

 careous nature. Lack of records of sufficient exploration makes 

 any statement purely tentative, but about seven to nine meters^ 



'C. A. Davis: "A Remarkable Marl Lake," Jour. Geol., Vol. VIII, No. 6. 



= Wesenberg-Lund : Lake-Lime, Pea Ore, Lake'Gytje. Saertryk af Medde- 

 lelser fra Dansk Geologisk Forening, No. 7, p. 156. 



