246 THE POPULAR SCIENCE MONTHLY 



Inquiry in Pittsburgh among metal workers developed the fact that 

 metal work in a smoky city lasts only half as long as in one free from 

 smoke. 



It is hardly necessary to point out that smoke damages the interior 

 decorations of a building or home, limits interior decorators in the use 

 of colore and materials and in every way tends to render artistic effects 

 gloomy and depressing. 



Cities very properly hold favorable climatic conditions as a very 

 desirable asset, as is evidenced by the records of rainfall, temperature, 

 fog and hours of sunshine which appear in the year books of the cham- 

 bers of commerce and boards of trade of the different cities. Cities 

 which have smoky atmospheres are under a severe handicap in this 

 regard. 



In the first place, while smoke is not a cause of fog, it intensifies a 

 fog when it is once formed and accordingly causes it to persist longer. 2 

 In consequence of this there are fewer hours of sunshine in smoky cities 

 than in cities which are practically free from smoke. Again, the sun- 

 shine is less intense in smoky cities, the light of short wave lengths, or 

 the blue light, suffering the greater depletion. Not only is this true, 

 but daylight, which depends entirely upon diffused light from the sky, 

 is depleted by the smoke in greater proportion than the direct sunlight. 



Experiments carried on by the Smoke Investigation of the Mellon 

 Institute in Pittsburgh and Sewickley, a small residential town on the 

 Ohio Eiver, about twelve miles northwest of Pittsburgh, during 1913, 

 revealed that Pittsburgh had 25 per cent, less sunlight and 40 per cent, 

 less daylight than Sewickley. It was also found that the limit of visi- 

 bility in the business section of Pittsburgh was about one tenth the limit 

 in the open country. It is well known that the frequency of intense 

 fogs in London has decreased and the hours of sunshine increased since 

 1890, due to a mitigation of the smoke nuisance. The same was true 

 of Pittsburgh between 1885 and 1895, when the use of natural gas for 

 manufacturing and domestic purposes was quite general. 



A number of studies have been made of the effect of soot on vegeta- 

 tion. Cohen and Euston, as a result of their researches in Leeds, Eng- 

 land, declared that soot may exert a detrimental effect on the growth 

 of plants in three ways, namely, by blocking up the stomata and thus 

 impeding the process of transpiration ; by coating the leaf and so reduc- 

 ing the intensity of sunlight, and at the same time affecting the assimi- 

 lation of carbon dioxide; and lastly, by the corrosive effect of the acid 

 it contains. 3 Experiments they carried on went to show that the power 

 of assimilation of laurel leaves had a definite relation to atmospheric 



2 Kimball, Herbert H., Bulletin No. 5, "The Meteorological Aspects of 

 the Smoke Problem," 1913. (Published by Mellon Institute.) 



s Cohen, Julius Berend, and Euston, Arthur G., ' ' Smoke : a Study of Town 

 Air," 1912. 



