153 



J. B. COHEN and A. G. RUSTON. The nature and extent of Air 



Pollution by Smoke. -- Nature, 81, 2085, Oct. 14, 1909, 

 pp. 468-469, figs. 2, London. 



Abstract of a paper read at the Health Congress at Leeds July 17, 

 giving the results of detailed examinations of samples of air taken 

 at 10 representative stations in Leeds and one at Garforth about 

 7 x / a miles from Leeds. 



" The impurities, in the form of suspended matter, consist of 

 soot, tar, sand, mineral substances, and, in solution, of sulphurous 

 and sulphuric acid or their salts, chlorides, largely in the form of 

 hydrochloric acid or common salt, and nitrogenous matter, in the 

 form of nitrates or free and albuminoid ammonia. " 



Injurious effects of these substances on vegetation are discussed. 



" It is the sulphurous acid which imparts to town fog its choky 

 and irritating effects. The large amount of this acid present in 

 fogs may be gauged from the fact that the hoar-frost collected 

 during the dense fog of January 27 (1909) contained acid corres- 

 ponding to 10.29 parts per 100 ooo, or more than ten times the 

 average acidity of the same station. " 



" To demonstrate the detrimental effect of sulphuric acid upon 

 vegetation, Timothy grass was sown on May 12, 1908, in boxes i 

 foot square, the soil being uniform. The seed was watered at a 

 rate corresponding to the average rainfall of 25 inches with water 

 containing different amounts of sulphuric acid. In addition to this, 

 three other samples were watered, with Garforth rain water in which 

 the acidity was neutralised, the second with ordinary Garforth 

 rainwater, and the third with Leeds rain water. The results were 

 instructive. In the case of Leeds rain water and of those waters 

 containing a high degree of acidity, germination was distinctly 

 checked, and the delicate green of the young grass quickly changed 

 to yellow or brown. Grasses watered with water containing 32 

 parts per 100 ooo were killed in a little more than three months, 

 and with 16 parts per 100 ooo in less than a year." 



" Chlorides are found in large quantities, especially in the in- 

 dustrial centres, where, expressed as common salt, they sometimes 

 reach as much as 3 or 4 cwt. per acre, a quantity which must be 

 distinctly prejudicial to vegetation. " 



" The nitrogenous impurities, on the other hand, would be be- 

 neficial by acting either as direct stimulants and fertilisers or by 

 neutralising the acidity of the sulphur and chlorine compounds. " 



