NOTES AND ABSTRACTS. 



645 



portions of such chimneys. The author suggests tliat soot should be 

 purchased by measure rather than by weight, as the hghter samples 

 are the richer, and the valuation varies inversely with the weight. He 

 points out also that where bought by weight four bushels should be 

 expected to the hundredweight, this being the minimum measure with 

 good domestic soot. 



Estimations are made of the amount of soot present in the atmo- 

 sphere of Leeds, as representing a manufacturing town, and it was 

 shown that the atmospheric content over the whole of Leeds would 

 correspond to some 220 tons for each square mile per annum, varying 

 from 25 tons in one of the residential portions of the town to 539 in one 

 of the industrial portions. 



There is also pointed out the effect of this material in the atmo- 

 sphere upon the sunlight, 17 per cent, more sunshine and 40 per cent, 

 more intensity of light being recorded at a point four miles outside the 

 town as compared with the centre. 



These facts are applied to the growth and development of plants in 

 various parts of Leeds, some figures being given showing the variations 

 in carbon-dioxide assimilation. Amongst the plants watched it was 

 found that in comparison with laurels growing in a residential part, 

 those in the polluted areas were stunted in size, and in the worst 

 districts were non-existent. 



An examination of the samples of soot indicated presence of mineral 

 acids to the extent, in certain parts, of as much as 80 lb. per acre 

 (presumably per annum). 



Ash trees were shown to retain their leaves six weeks longer in the 

 purer parts of Leeds than in the more contaminated districts. 



Its effect upon crops is referred to, showing that the yields over a 

 given area of radishes and lettuces in one of the contaminated districts 

 were only from one-quarter to one-half that obtained under the better 

 conditions further out. 



Particulars are also given of some experiments made to estimate 

 the deposit of tar amongst the soot, such tar of course choking up the 

 stomata on the leaves with bad effect. The annual deposit of tar for 

 each square mile was shown to vary from 4| cwt. to 110 cwt., the 

 lower figure being in a residential part, and the higher figure in an 

 industrial one. — W. A. V. 



"Sooty Blotch," A new fungus disease of Apples. By E. S. 



Salmon {Gard. Chron., xlviii., p. 443; Dec. 17, 1910; 2 figs.).— The 

 3ause of " sooty blotch " is said by the writer to be a species of 

 heptothyrium not previously recorded for this country. The blotches, 

 vhich are more or less rounded, one-fifth of an inch or less in 

 diameter, are composed of the straggling hyphse of the fungus. On 

 he same apples minute black spots were found. This condition is 

 aiown as " fly-speck " in America. In Professor Duggar's book 

 ' sooty blotch " and " fly-speck " are ascribed to the same cause, 

 iz., Leptothyrium, but F. L. Stevens and J. G. Hall ascribe 



