150 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, C0 2 in the 

 imperial gallon. 

 ,~g, f Maximum ... . 23*0 

 ' 1 Minimum .... 9*3 



1862.1 



CaO,C0 2 inthe 



imperial gallon. 



Maximum .... 21*8 



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. 



1. 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 Eeport on the Supply of Water to the Metropolis, June 17, 

 1851, fry Messrs. Graham, Miller, and llofmann ; and Quarterly Journal of the 

 Chemical Society, vol. iv. p. 381. 



