NOTES AND ABSTEACTS. 



615 



and observations upon the effects of certain classes of atmospheric 

 impurities upon vegetation. 



It was found that the total amount of nitrogen (ammonia and nitric 

 nitrogen) brought down by the rain (26.95 in. per annum) at Garforth 

 was 8.37 lb. for each acre per annum. This is greatly in excess of the 

 average at Eothamsted, which is 3.84 lb. with an almost identical rain- 

 fall. A further quantity of nitrogen (about 1.5 lb.) was brought down 

 in the organic matter. . 



Of sulphur the average annual precipitation was 95.7 lb. SO3 to 

 each acre, about five times the Eothamsted average. 



Chloride was brought down at an average of 20.89 lb. to an acre. 



20.05 lb. of free acid was precipitated on each acre per annum, 

 the acidity during foggy weather being remarkably high, and the 

 winter rain (owing largely to fogs) being much more acid than the 

 summer. 



The air of Garforth (in an agricultural district) is thus polluted to a 

 remarkable extent, and this suggested a comparison with the air of 

 Leeds. Ten stations were selected in places varying from one another 

 as much as possible. The amount of matter in suspension varied with 

 the kind of industry carried on, being naturally heavier in the coal- 

 mining and industrial centres than in the suburbs. The greatest pollu- 

 tion of this kind amounted to 1,900 lb. to an acre in one case and 

 1,500 lb. in another, while it was only 90 lb. in the station furthest 

 from the centre of the city. In the worst districts the ash amounted 

 to 60 per cent, of the suspended matter; in the suburban districts to 

 only 45 per cent. The suspended matter was rendered more objection- 

 able by the great amount of adhesive " tar " which it contained. It 

 is remarkable that this amounted to only about 5 per cent, in the con- 

 tamination arising mostly from the factories and to about 16 per cent, 

 in that arising mainly from the domestic range. In the most polluted 

 area the soot deposited amounted to 840 lb. to each acre annually, and 

 to only 27 lb. at the station furthest from the centre of the town. 



The presence of this suspended matter in the atmosphere has a 

 marked effect upon the number of hours of bright sunshine experienced. 

 In the centre of Leeds it amounted to only 1,167 as compared with 

 1,402 at Adel, Tour miles north. 



The amount of free acid precipitated was not always proportional 

 to the amount of contamination, for alkaline matters are often produced 

 by the factories, and the amount of sulphur brought down did not vary 

 greatly from that observed at Garforth. Chlorine was, however, greatly 

 increased, amounting to 200 lb. per annum at one station. Nitrogen 

 was also increased to 18| lb. in the most polluted area. 



Tables are given showing the effect of atmospheric pollution upon 

 the intensity of the light, and, as the authors point out, its stunting 

 effect upon the little vegetation that survives is very marked. But in 

 addition to this the leaves become coated with a thick black deposit 

 which further checks the incidence of light and which from its adhesive- 

 ness tends to block the stomata. Eain is not effective in removing these 



