254 ON THE PURIFICATION OF DRINKING WATER. 
stances. One of the seeds is well rubbed for a minute or 
two round the inside of the vessel containing the water, 
generally an unglazed earthen one, which is then left to settle, 
In a very short time the impurities fall to the bottom, leaving 
the water clear, and so far as I have been able to learn, per- 
fectly wholesome. These seeds are constantly carried about 
by the more provident part of our officers and soldiers in time 
of war, to enable them to purify their water. They are 
easier to be obtained than alum." 
Dr. O'Shaughnessy suggests that the clearing action 
depends on astringency in the fruit. But even if there 
were an astringent principle present, it would not account 
for the effect. We believe the efficacy depends on the pre- 
sence of albumen and casein in the seed, which act as fining 
agents, like those employed for wine and beer. If the seeds 
be sliced and digested in water, a thick, mucilaginous ropy 
liquid is obtained, which, when boiled, yields a coaguhun. 
If this be removed, a further coagulum is obtained, by the 
addition of acetic acid. These reactions show the presence 
of albumen and casein. 
If this opinion be well founded, many other seeds ought 
also to have a similar influence; and this really appears to 
be the case. Thus we are told that, in order to clarify the 
muddy waters of the Nile, the natives of Egypt rub the 
inside of earthen jars, in which the water is kept, with 
almonds prepared in a particular manner. The water is 
then strongly agitated, and afterwards covered, and allowed 
to remain at rest for four or five hours, at the end of which 
time the impurities have subsided, and the supernatant 
clarified water is decanted. 
Niebhur says bitter almonds are used; but Dr. Arcet 
states that either bitter or sweet almonds may be em- 
ployed. They are peeled, and made into cakes as large as 
eggs. 
At Sennaar and Dongola, in Nubia, beans, haricots, and 
even castor seeds are also used for clearing the water of 
