VICTOR E. SHELFORD. 

 TABLE 1 1 . 



SHOWING K.INIIS ANI> AKKA* 01- H..IIMMV 



It will be noticed that the area of sand is much less in tin- older 

 ponds and the area of humus much greater, due to accumulation 

 of the latter from the decay of vegetation. The depth of humus 

 does not increase proportionately with age because it becomes 

 more compact with time. With the exception of the first pond, 

 the average depth of humu> \va> obtained by dividing the average 

 depth at the center by two. In the case of pond i, then- are 

 large areas with only two centimeters of humus and two deep 

 places which contain humus of considerable depth ; we give only 

 an estimate. 



(c) The Dissolved Content of the Water. For a preliminary 

 study of the dissolved solids of the water we have had a single 

 analysis of the solids and four analyses of the ga^-^ made by 

 chemists, (i) Solids. The small value of single analyses of solids 

 is well known; sanitary analysts have pointed out the danger,^ 

 arising from conclusions drawn from so little data. Ho\\ever, in 

 this particular case, the value of the roiilts is greater than in tin- 

 case of single analyses of drinking water, because of the following 

 conditions in and about the ponds. 



(a) The ponds are without outlet and have no >t i vam> cmpi yin.^ 

 into them. 



(b) During rain they have little inwash because nearly all water 

 must filter into them through sand; in case rain falls in such tor- 

 rents as to actually run in from the >ides tin- area of drainage is 

 small, being a strip not more than fifteen meters wide on either 

 side of each pond. The ponds than are comparable to balanced 

 aquaria and any variation of dissolved solids muM be due in tin- 

 main to the effect of organisms, of evaporation, and of renewal 

 from rain. 



It -hould be noted that these analyses were made at i he end <>\ 



