The smoke-clouds of our cities influence a number of weather states which affect human conduct. The meteorological conditions particularly affected are: sunshine, clouds, humidity, fogs, temperature, electrical potential and luminosity. That the smoke from factory and domestic fires, by filling the atmosphere with opaque clouds of smoke and by inducing mists and fogs, deprives the city dwellers of the luminous, vitalizing, cheering, health giving, germicidal rays of the sun, has been proved by numerous observations and tests. It has been computed that seven-eighths of the sun’s power is shut out by the smoke in the manufacturing center of London, and five-eighths in Westminster. The percentage of sunshine in these two places compared with the rural stations of Oxford, Cambridge, Marlborough and Gildiston was found to be as follows (12): TABLE I. Winter Summer From 1881-1885: 17% 83% ” 1906-1910: 38% 92% It is observable that the amount of sunshine suffers an enormous reduction in the winter time but only a very slight diminution in the summer, and that during the last five years the conditions have considerably improved, due, as we are told, to the considerable abatement during the last decade or two of London smoke. During one calendar year the hours of sunshine in the center of Leeds amounted to 1164 while the corresponding figure for Adel, which is only 4 miles distant, was 1402 (4). Thus the loss of sunshine in Leeds due to smoke amounted to 17%. The diminution of sunshine in towns near smoke-producing cities is, again, shown in the following tabulation of the comparative monthly average duration of bright sunshine for a period of 20 years (24): TABLE II. Station Nov. Dec. Jan. Feb. Runhill Row 22.8% 7.5% 14.1% 30.5% Westminster 27.7% 13.1% 18.4% 32.8% Kew 50.8% 38.1% 40.3% 54.6% Cambridge 61.0% 40.6% 48.9% 72.8% At Kew, seven miles west of London, the reduction of sunshine due to the London smoke has been placed at 37% for a whole year. In the United States of America for the decennium, 1901-1910, the aggregate hours of sunshine, percentage of possible sunshine, number of cloudy days, number of partly cloudy days, and number of foggy days have been found by the Pittsburgh smoke investigators, from a study of the records gathered by the United States Weather Bureau in various cities throughout the country, to be as shown in Table III. TABLE III. STATISTICS OF SUNSHINE IN 18 CITIES OF THE UNITED STATES 1. 2. 3. 4. 5. 6. Aggregate Percentage No. of No. of No. of Total hrs. of of possible cloudy partly foggy of 3 Station. sunshine. sunshine. days. cloudy days. and 4. days.