192 Mr. Warmgion on Alteratiori of Carbomte'Of--Lime [Dec. 5, 



The data tlius obtained will help to elucidate several very important and 

 interesting phenomena in respect to all the three elements of the arrange- 

 ment — the water, the fish, and the vegetation. 



I. The Water. 



The importance of growing submerged vegetation in maintaining waters, 

 rich in carbonate of lime, in a meliorated state by diminishing their hard- 

 ness has been clearly demonstrated by the foregoing data ; and how neces- 

 sary, therefore, it is that this association should be kept in view whenever 

 a soft and healthful water is required for domestic purposes. Unfortunately 

 this appears hitherto not to have been well understood, or at all events has 

 been little attended to, since the very agent which has been provided na- 

 turally for effecting these beneficial results has been most commonly 

 regarded as an evil, and studiously eradicated in all directions. These data 

 will also explain the cause of the rapid growth of vegetation in well-waters 

 rich in carbonic acid, when pumped into tanks or reservoirs and exposed to 

 the full light of day. The plant-germs, naturally contained in the water 

 or absorbed from the atmosphere, being supplied with an abundance of ap- 

 propriate nourishment, rapidly vegetate, and the containing vessels, parti- 

 cularly during the summer months, soon become thickly coated with a 

 dense confervoid growth. 



It will also follow that all fish, as generators of carbonic acid, should be 

 excluded from waters flowing over carbonate-of-lime strata, and intended 

 for the supply of towns &c., as tending to increase their hardness. Of 

 course the absence of calcareous matter would prevent such an effect taking 

 place — a fact borne out by the well-known softness of springs and rivers 

 flowing out of or over granite or sandstone rocks, even when thickly inha- 

 bited by the scaly tribe. 



2. The Fish. 



It is well known that water has the property of absorbing air from the sur- 

 rounding atmosphere, and holding it in solution to the extent of from one- 

 fortieth to one- thirtieth of its volume, not, however, without somewhat 

 changing the proportion of its constituents ; for when the absorbed air is 

 abstracted from water it usually contains about thirty-two per cent, of oxy- 

 gen gas, instead of twenty-one. This oxygen is converted by the respiration 

 of the fish into carbonic acid, which is held dissolved by a still stronger 

 afiinity, the water being capable of retaining as much as its own volume 

 of this gas in solution at the ordinary temperature and pressure of the 

 atmosphere. 



In the above- described arrangement the carbonic acid thus produced is 

 absorbed by the submerged vegetation under the influence of the sun's 

 light ; the carbon is appropriated for its growth, while the oxygen is again 

 liberated and hela in solution by the water, provided the evolution is not 

 too rapid, an effect produced by too great an exposure to the sun's light. 

 When this is the case, much of the oxygen necessarily escapes into the air 



