194 On Alteration of Carhonate-of -Lime Waters. [Dec. 5_, 



215 cubic inches of that gas in the ten gallons of water, or more than y^th 

 its volume. The exact numbers will be seen in the following Table : — 



CaO, CO2 in the gallon. CO.. 

 ,4,^, J Maximum 23*0 grains, requiring 10-120 grains to form CaO,2C02. 

 ^^^^ I Minimum 9-3 „ „ 4 092 „ 



J gg,-, I Maximum 21-8 „ „ 9-592 „ „ „ 



'[Minimum 8-8 „ „ 3-872 „ „ „ 



Carbonic acid required to dissolve the increase 6*248 grains = 13*269 cub. in. 



,, minimum 3-872 8*228 ,, 



10*120 „ 21-497 „ 



Yet, although the quantity of poisonous gas had been thus increased, we 

 find no deleterious action on the health of the fish, no disturbance in the 

 ordinary respiration, no gulping at the surface of the water for fresh air. 

 It is q*aite evident, therefore, that the carbonic acid, by entering into com- 

 bination with carbonate of lime, however weak that combination may be, 

 is thereby rendered perfectly innocuous, and a wonderful provision is 

 thus afforded for preventing this poisonous agent from becoming fatal to 

 animal life. 



We turn now to the next member of our arrangement. 



3. The Vegetation. 

 It will be seen from the foregoing numerical results that the inaximum 

 quantity of dissolved carbonate of lime, and consequently of carbonic acid, 

 is found just before the period of the reviving energies of the plant's growth, 

 namely, the spring time of the year, when the days are lengthening and the 

 sun's light is continually increasing in strength ; the minimum quantity 

 when this growth has attained its greatest exuberance, namely, when the 

 summer months are past and the light is beginning to decrease in its in- 

 tensity and the days to shorten. So exactly, indeed, are the energies of 

 the plants regulated by the amount of light to which they are exposed, that 

 a constant arrangement, such as that here described, affords an excellent 

 indication of the variation of the seasons in different years, or might even 

 be made a rough measure of the total amount of light from month to 

 month. 



But while the demand for carbonic acid on the part of the plant varies 

 in this manner with the seasons, the amount of that gas produced by the 

 respiration of the fish is very nearly the same all through the year. Whence, 

 then, does the plant obtain that additional quantity of food which its 

 stimulated energies require during the spring and early sum.mer months, 

 and which its rapid and luxurious growth show to be readily supplied ? 

 After what has been stated, I think the souj-ce must be apparent to every 

 one — it is from the carbonic acid which has been gradually accumulated, 

 and rendered innocuous to animal life from its being held in combination 

 with carbonate of iime^ in so marvellous a manner during the winter 



