70 PROCEEDINGS OF THE AMERICAN ACADEMY 



Its sedimentary deposits may contain the remains of both fresh and 

 saline water forms of life within the same area, thus offering an inter- 

 esting subject to the observation of the naturalist. 



Chemically considered, these two differing masses of water in con- 

 tact exert powerful action. The organic matter suspended and dis- 

 solved in the fresh water, brought into contact with the saline water, 

 leads to a number of decompositions of compound bodies. All the 

 phenomena exhibited by ocean water in contact with water passing 

 through the earth and entering the sea below its surface, are seen in 

 this pond most distinctly. Thus, the sulphate of lime becomes decom- 

 posed into a salt composed of hydrosulphuric acid and lime, this new 

 salt reacts on oxides of the common metals to produce sulphides and 

 carbonate of lime, or upon sulphates of alkalis, so as, in presence of 

 an excess of carbonic acid, to produce carbonate and bi-carbonate of 

 soda, which may enter into new forms of matter. A bright metal 

 plate immersed in this water at a certain depth may be exposed for 

 hours to the action of the water without change. But if the slip 

 be allowed to pass deeper, so as to reach the saline water, in the 

 lapse of a few minutes it becomes coated with sulphide of the metal. 

 The engineers engaged in the observations on the pond lowered a 

 long silvered slip of copper vertically, so it should pass through the 

 mass of fresh and saline water. On withdrawing the slip, after some 

 hours had elapsed, the line of contact of the masses of waters was 

 permanently marked on the slip, — all above it was unaltered, all 

 below was blackened on the copper side by the formation of sulphide 

 of copper. It was extremely interesting to note that the band pre- 

 sented no gradation of chemical action. Within the distance of one 

 fourth of an inch, action and no action were marked, and it was in 

 this way, as well as by chemical analysis, that the fact of the masses 

 preserving their places was learned. Down into the fresh water, to 

 within twelve inches of the saline water, the taste does not indicate 

 the slightest saline taint, and even nearer the mass which produces 

 so powerful chemical changes, the water is nearly pure. There is 

 manifested in this juxtaposition of two watei's of unlike composition 

 some of the minor effects of electrical action, and in considering the 

 chemical changes which may be and are exhibited in consequence, 

 it appears that such a condition would be sufficient to account for 

 the production of many bodies, which have been supposed to result 

 from more active agencies only. 



