54 Nature of Aquatic Environment 



lake to the blood of the animal body. As the cells of 

 the body take from the Mood such of its content as is 

 suited to their need, so the plants and animals of the 

 water renew their substance out of the dissolved sub- 

 tin- water brings to them. 



ante substances dissolved in the water may so 

 i I n »tli its density and its viscosity as to determine 

 both stratification and distribution of suspended solids. 

 This is a matter that has scarcely been noticed by 

 limnologists hitherto. Dr. J. U. Lloyd ('82) long ago 

 sin wed how by the addition of colloidal substances to a 

 vessel of water the whole contents of the vessel can be 

 1 >r< >ken into strata and these made to circulate, each at 

 its own level, independent of the other strata. Solids 

 in suspension can be made to float at the top of particu- 

 lar strata, according to density and surface tension. 



Perhaps the "false bottom" observed in some north- 

 ern bog-bordered lakes is due to the dissolved colloids 

 of the stratum on which it floats. Holt ('08, p. 219) 

 ribes the "false bottom" in Sumner Lake, Isle 

 R< >yal, as lying six to ten feet below the surface, many 

 f< ■ t above the true bottom; as being so tenuous that a 

 p< >le could be thrust through it almost as readily as 

 through clear water; and as being composed of fine 

 disintegrated remains of leaves and other light organic 

 material. "In places there were great breaks in the 

 'false bottom,' doubtless due to the escape of gases 

 which had lifted this fine ooze-like material from a 

 greater depth: and through these breaks one could 

 look down several feet through the brownish colored 

 water." 



Perhaps the colloidal substances in solution are 

 such as harden upon the surface of dried peat, like a 

 water-proof glue, making it for a time afterward imper- 

 vious to water. 



