159 
surface layers of the soil partly accounts for the higher 
figure in the albuminoid ammonia, so that there is no doubt 
whatever that the permissible limit of albuminoid ammonia 
should be much higher in the East than in the West. Thus 
quite a large number of well-sunned and pure lake waters 
would be condemned on their high albuminoid ammonia 
figure, whereas certain shallow wells, whose bacteriological 
analysis shows that they contain a large number of most 
undesirable fecal bacilli, would be passed because the free 
and saline ammonia are low, and the nitrates high. Chemical 
analysis in a tropical water, particularly as regards organic 
nitrogen, is not of very much use by itself, and if possible 
water should never be judged on this alone. Chemical 
analysis however should always be carried out in order to ascer- 
tain the mineral impurities. Many of the waters in India, 
particularly those from wells and springs, are extremely hard. 
The Madras well waters seldom contain less than 25 parts 
per 100,000 and many othersas highas 80 parts per 100,000 
of total hardness, much of which is temporary. Apparently 
the natives of India are not easily upset by this degree of 
hardness, though many Europeans take time to get accus- 
tomed .to it. 
The surface waters are usually soft in the rainy weather, 
but on account of the amount of subsoil drainage which 
goes on into the rivers in the dry weather, the hardness not 
infrequently greatly increases at this time. For instance, 
the hardness of the water of the Hooghly at Calcutta in the 
rains 1s about 2 to 3 parts per 100,000, but it rises to 18° in 
the dry weather. These are the most important points in 
connection with the chemistry of surface water. 
