CHEMICAL SCIENCE. 217 



The Influence of Drainage on Public Health. A remarkable in- 

 stance of the influence of town drainage on the public health is shown 

 in a report which has just been issued by the sanitary committee of 

 the Halifax corporation in England. Great sewerage works have 

 been constructed since 1851, and between that period and the pres- 

 ent the death-rate has decreased from 25.39 per 1,000 to 21.48 per 

 1,000. ^ This is in the town of Halifax itself; in the " Union " the 

 mortality has only decreased 1^ per cent., a fact which shows more 

 clearly the beneficial operation of the sanitary improvements in 

 Halifax. 



SEWAGE OF CITIES. 



In a paper recently presented by Prof. Voelcher to the Royal (Eng.) 

 Agricultural Society, on the above subject, the author stated that 

 the general conclusion he had arrived at was, that although sewage 

 manure is very desirable for grass crops, it was next to useless for ara- 

 ble land or green crops, or even for market gardens. The value of 

 sewage could only be ascertained experimentally on the field. Pres- 

 ent experience only went to show that, according to the soil and other 

 conditions, the town sewage of Edinburgh, which is rather more con- 

 densed than that of London, was worth only from one-half pence to 

 one and a quarter pence per ton. In applying sewage, it was better 

 to allow the deposit of suspended matters, and use only the clear 

 liquid. As he bad said, the only crops to which they could apply 

 sewage to advantage were grass crops, and then it must be applied in 

 great quantities and at the particular time when it was required. It 

 should be applied, if possible, by gravitation and open irrigation, for 

 no soil had the power of laying up in its body the greater part of the 

 soluble fertilizing constituents. On poor sandy soils, the excrernenti- 

 tious matters of sewage were of great utility ; but in reference to 

 good clay soils, water was the most valuable portion of the sewage, 

 the fertilizing matters being in that case of little or no importance, in 

 fact hardly worth calculating ; whereas, on light, poor, sandy soils, 

 the value of sewage rose or sank with the amount of fertilizing mat- 

 ter applied to the land. So far from sewage being a great fertilizer 

 of vegetable gardens, it certainly would not pay for the machinery 

 and pipes necessary to bring it even from a short distance, and spread 

 it on the ground. Anything that was grown very quickly was in- 

 ferior in quality to the same kind of thing which was grown more 

 slowly. Quickly-grown grass, for instance, was far more crude than 

 that which was grown slowly extreme rapidity of growth being 

 always attended by inferiority of quality ; but, of course, it was quite 

 another thing whether it was not more profitable to producers to 

 have the large increase in quantity, although it was attended by some 

 degree of inferiority. 



SEWER DEODORIZATION BY CHARCOAL FILTERS. 



The investigations of Dr. Stenhouse, of London, in respect to the 



action of charcoal in deodorizing foul gases, etc., are generally well 



known. In a paper, however, recently communicated to the London 



Society of Arts, he gives a resume of the opinions and results which 



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