468 



NA TURE 



[October 14, 1909 



North America and Siberia, but some more southern 

 stations are included. 



Without going into any great detail, the mvestigation 

 may be sunimarised as follows. Prof. Hildebrandsson re- 

 gards the state of the ice of the polar sea as being the 

 principal cause of the different types of the seasons of 

 different years. Thus a high summer temperature in the 

 arctic sea to the north of Europe will set free a large 

 amount of ice, and consequently the polar current arriving 

 on the north coast of Iceland in February and March, and 

 a branch of which, after skirting the east coast, is directed 

 towards the North Sea, will bring much ice and will be 

 surrounded by a layer of cold water. This current will 

 cool the air in its neighbourhood. The result of the 

 movement southward of these specially cold currents is 

 that the land areas around the Arctic Circle and North 

 Atlantic Ocean suffer mcccss'wely from them by the lower- 

 ing of their air temperatures. Prof. Hildebrandsson 

 accompanies his statements with tables and an excellent 

 series of curves, which are very convincing. He specially 

 refers to the investigation of M. Peterson, who showed 

 that a variation of 2° or 3° in the surface temperature 

 of the sea is sufficient to create changes of considerable 

 magnitude in the air temperature over very large areas. 



The main result of this research is to indicate that in 

 certain cases a means is afforded of making forecasts for 

 seasons. Thus, to take an example, he shows that, with 

 two or three exceptions, in twenty-five years the tempera- 

 ture of the summer at the North Cape was in the follow- 

 ing spring in opposition to that of Europe, represented by 

 Debreezin. 



THE NATURE AND EXTENT OF AIR POLLV- 



TION BY SMOKE A 

 TN a former paper read at the Congress of the Sanitary 

 ■'■ Institute held at Leeds in 1897 an account was given 

 of the quantity of soot suspended in and deposited from 

 the atmosphere of Leeds. It was then shown that, on the 

 average working day, 20 tons of soot are sent into the 

 air of Leeds, of which half a ton falls on an area of four 

 square miles, and of the latter from 20 lb. to 25 lb. stick, 

 that is, are not removable by rain. The present paper 

 contains a record of the atmospheric impurities carried 

 down by rain and the effect of this rain water on vegeta- 

 tion. It also contains an inquiry into the diminution of 

 daylight caused by suspended particles of soot. 



Ten representative stations were selected in Leeds and 

 one at Garforth, about yJ- miles due east of Leeds. _ The 

 impurities, in the form of suspended matter, consist of 

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

 sulphurous and sulphuric acids or their salts, chlorides, 

 largelv in the form of hydrochloric acid or common salt, 

 and nitrogenous matter, in the form of nitrates or free 

 and albuminoid ammonia. The results are embodied in 

 the following table : — 



Analyses of Raix' Water, Leeds and Garforth. 

 Total for Year, expressed in Pounds per Acre. 



The solid impurities were found to diminish rapidly in 

 passing northwards from the centre of the town. Within 

 the distance of a mile the quantity fell to less than half, 

 and at 2* miles to less than one-fifth. 



The influence of the industrial centres upon the solid 

 impurities stands out most conspicuously, as a glance at 

 the table will show, i.e. in the chief industrial centres the 

 solid impurities are roughly twenty times as great as_ in 

 the purer atmosphere of Roundhay, about three miles 

 north-east of the centre of the town (Fig- i)- 



The quantity is also determined by the prevailing winds, 

 which are west, south-west, and north-east, and the drift 

 of the impurities is consequently more towards the east 

 than the west. Of thij three constituents of the_ total 

 suspended matter, the one which is least injurious is the 

 mineral matter. This is abnormally high at the Leeds 

 Forge, and consists principally of oxides of iron, lime, 

 alumina, and silica, either escaping with the fumes from 

 the furnace or thrown out mechanically. 



In a former series of experiments the amount of soot 

 deposited was determined by collecting daily from a fresh 

 surface a square yard of snow (which lay for several days), 

 melting, filtering, and weighing the soot. The total 

 deposit on the first day represented i6 cwt. to the square 

 mile, and the daily increase was, on the average, 4 cwt. 

 Taking a four-square-mile area covered by the town, and 



1 Abstract of a paper by Prof. J. B. Cohen and Mr. K. G. Ruston read at 

 the Health Congress held at Leeds on July 17. 



NO. 2085, VOL. 81] 



I.LEEDS FORCE 



2.HUNSLET 



8.BEEST0N HILL 



4. PHI LOSOPM IC A L HA L L 



5.HEADINGLEY 



8.ARMLEY 



7. OBSERVATORY 



8. KIRKSTALL 

 9.WEETW00DLANE 



1. ROUNDHAY 



128458789 ll> 



Fig. I. — Suspended Matter, 



allowing for a diminishing fall on the fringe of the area, the 

 amount carried down by the first fall of snow may be re- 

 presented roughly by 10 cwt. to the square mile, and the 

 daily increase as one quarter of this amount. Later results, 

 as determined from the soot deposited w-lth the rain water, 

 are in close agreement with these figures. The analyses of 

 the total deposit for the whole year show that at Hunslet 

 (industrial centre) the .soot amounts to 300 tons per square 

 mile, at the Leeds Forge (industrial centre) to 250 tons, 

 whereas at Woodhouse Moor (one mile north-west of the 

 centre) it dropped to So tons. Taking the average of 

 the stations which lie within the central four-square-mile 

 .'■.rea, we get 190 tons per square mile per year, or roughly 

 half a ton per square mile per day. 



Uhe amount of tar deposited with the soot was previously 

 demonstrated by exposing glass plates i foot square at 

 different points situated in and at distances from the town. 

 These plates at intervals were washed under running 

 water, and the residual deposit analysed. The amount of 

 soot thus remaining, as determined from its carbon con- 

 tent, was found to be twenty-four times greater in the 

 town than at a distance of nine iniles. In the present 

 experiments the tarry matter was estimated by extraction 

 with ether. The quantity dropped from 80 lb. per acre 

 per annum in the centre to 14 lb. per acre at a distance 



