150 Royal Society. 



acid contained in a saturated aqueous solution is entirely displaced 

 by a current of atmospheric air passed through it for five minutes ; 

 and also * that, by the same means, a solution of carbonate of lime, 

 in water previously saturated with carbonic acid, will have all the 

 excess of gas displaced in fifteen minutes, leaving the water with 

 bicarbonate of lime in solution. It is in this form of combination 

 that MM. Peligotf and Pogglale J consider the carbonate of lime 

 to exist in the water of the Seine, and M. Bineau § in that of the 

 Rhone, in which rivers they state there is no free carbonic acid. In 

 the present investigation we shall therefore assume it to be in the 

 same state of combination. We have, in the series of experiments 

 detailed above, an increase in the quantity of carbonate of lime held 

 in solution, amounting to 142 grains in the imperial gallon, which 

 would require nearly Q\ grains of carbonic-acid gas to dissolve it. 

 Besides this there is also the quantity already present in the water 

 at its minimum, which amounts to nearly four grains more, or in 

 all to about ten grains, equal to nearly 215 cubic inches of that 

 gas in the ten gallons of water, or more than j^ih. its volume. The 

 exact numbers will be seen in the following Table : — 



CaO, CO^ in the gallon. CO.^. 



^ J Maximum 23-0 grs,, requiring 10120 grs. toform CaO,2C02. 



J Ma 

 JMi 



nimum 9-3 „ „ 4092 



^^ , Maximum 21-8 „ „ 9-592 „ 



^"^^ I Minimum 8 8 „ „ 3-872 „ 



Car, acidrequiredtodissolve the increase 6-248 grs. = 13-269 cub. in. 

 „ „ minimum 3-872 „ 8-228 „ 



10-120 „ 21-497 „ 

 Yet, although the quantity of poisonous gas had been thus in- 

 creased, 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 quite evident, therefore, that the 

 carbonic acid, by entering into combination with carbonate of lime, 

 however weak that combination may be, is thereby rendered per- 

 fectly 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 

 maximum 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 



* Op. cit. vol. iii. p, 7. 



t Comptes Rendus, vol. xl. p. 1121, and Bischofs 'Elements,' vol. iii. p. 117. 

 \ Journal de Pharmacie, vol. xxviii. p. 321, and op. cit. vol. iii. p. 118. 

 § Comptes Rendus, vol. xli. p. 511, and op. cit. vol. iii. p. 118. 



