148 Royal Society :—Influence of Animal 
To determine how much was the next point for investigation. 
Portions of the water were taken on several occasions and boiled 
for a considerable time, filtered, and the volume restored to its 
original bulk with distilled water. On examining these portions 
with the soap-test, it was found that the hardness was lowered to 
5°6 degrees, equivalent to 5°6 grains of carbonate of lime. But 
inasmuch as carbonate of lime is soluble in water to the extent 
of 2:4 grains in the imperial gallon*, this will be reduced to 3:2 
grains, which amount will therefore have to be deducted from each 
of the above results, in order to arrive at the true quantity of car- 
bonate present in solution. 
The maximum and minimum results will then stand thus :-— 
CaO, CO, in the CaO, CO, in the 
imperial gallon. imperial gallon. 
1861 | aidiancn Te ere 1862 Maximum.... 21°8 
"| Minimum .... 9°3 "| Minimum .... 8°8 
The data thus obtained will help to elucidate several very im- 
portant and interesting phenomena in respect to all the three 
elements of the arrangement—the water, the fish, and the vege- 
tation. 
l. The Water. . 
The importance of growing submerged vegetation in maintaining 
waters, rich in carbonate of lime, in a meliorated state by dimi- 
nishing their hardness has been clearly demonstrated by the fore- 
going data; and how necessary, therefore, it is that this association 
should be kept in view whenever a soft and healthful water is re- 
quired 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 naturally 
for effecting these beneficial results has been most commonly re- 
garded 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 reser- 
voirs and exposed to the full light of day. The plant-germs, natu- 
rally contained in the water or absorbed from the atmosphere, being 
supplied with an abundance of appropriate nourishment, rapidly 
vegetate, and the containing vessels, particularly 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 inhabited by the scaly 
tribe. 
* Chemical Report on the Supply of Water to the Metropolis, June 17, 
1851, by Messrs. Graham, Miller, and Hofmann; and Quarterly Journal of the 
Chemical Society, vol. iv. p. 381. 
