214 Mr. Waldie’s investigations connected [No. 3, 
It may be useful to refer for the purpose of comparison to the 
composition of some other waters supplied to towns, and I shall take 
for that purpose one of the most recently published reports on the 
subject, namely, that by Professor Frankland on the water supply of 
London during the year from February 1865 to January 1866.* 
The only points determined connected with the mineral consti- 
tuents are the total amount of saline matters and the amount 
of earthy salts as ascertained by the soap test ; this, as is well known, 
being the application of the familiar fact that hard water curdles 
soap, to ascertain its purity; a solution of known strength of soap 
being added to a measured quantity of the water to be examined 
from a graduated tube, until the curdling effect of the salts of lime and 
magnesia which cause the hardness is exhausted, and the water produces 
a lather on shaking. The quantity of soap required indicates the 
amount of earthy salts present ; an easy and speedy means of obtaining 
a sufficiently good estimate of the amount of earthy salts in water. 
By deducting from the total solid matter first the amount of organic 
matter, the total inorganic is obtained; and by deducting from this 
the amount of carbonate of lime, the remainder will indicate, with 
sufficient approximative accuracy, the amount of alkaline salts. Here 
are the results of this proceeding —for the waters of 
Five Thames New River Kent and 8. 
Companies and River Essex Co.’s 
average. Lea. Artes. Wells. 
Total solid matters, mean 26.63 26.11 39.08 
Deduct organic and volatile, mean 1.60 1.30 1.73 
25.03 24.81 37.30 
Carbonate of Lime 17.69 20.65 25.16 
Alkaline salts 7.34 4.16 12.14 
It will be observed that the alkaline salts are in much larger 
proportion to the earthy carbonates than in the Hoogly water, this 
being specially the case in the Artesian well waters. The waters of New 
River and River Lea come nearest the Hooghly. The amount of solid 
matter is much greater in the average than that of the Hooghly river 
* Jourval of the Chemical Society, June 1866, 
