IVeat/ier, IVatfr and Disease. 19 



no case of depression of teniperatnre not followed b\- increase 

 of death rate. Two English writers, in the P'ebruary number 

 of the " Contemporary Review," say : " The painful irritation 

 to the eyes, the choking sensation in the chest, together with 

 the general depression of the spirits and many other ailments, 

 are the lesser sufferings that few who are exposed to it escape. 

 But it is not yet realized what an amount of serious illness, or 

 how many deaths one week of London fog causes. It may be 

 accepted that every ten days of this terrible visitation kills 

 2,500 people, and if we calculate nine serious cases of illness 

 to each death, we have near 25,000 laid upon beds of sickness." 



On plant life the effect of town fogs is great. At Kew gar- 

 dens and hot houses, plants inside of some cover were pre- 

 vented from growth. " Bushels of healthy looking leaves 

 were picked up almost every morning. There is al.so great 

 absorption of light by fogs. The .slower vibrating red rays 

 can struggle through a fog which is absolutely impervnous to 

 the more refrangible ones. A mist but slightly tinged with 

 smoke is opaque to the blue rays, but heat rays pass readily 

 through." The shutting out of the blue rays cuts off the 

 most active chemical ones. The number of sunshine hours 

 counted at five stations, one in the heart of the city of lyon- 

 don, and others not far from the city, were as follows : In 

 November, December, January and February 95.8 in the city, 

 at the others 150, 17, 17, 205.9 and 26S.3. It will be seen that 

 fog, as a factor in weather, may Vjecome injurious to health b}- 

 interfering with the action of light, bj- the retention of exces- 

 sive quantities of carbonic acid, which would otherwise 

 escape, by the low temperature which accompanies it, and by 

 the much reduced number of sunshine hours, and by encour- 

 agement of bacterial growths, or rather preventing the noxious 

 effect of sunlight on those already in the air. 



The next factor of air as an agent of disease is the bacterial. 

 Here we enter a field where acute and accurate scientific 

 methods have the most successful illu.strations. The effect 

 has been that the germ theory is almost common knowledge. 

 P'or over 200 years it has been at times within the horizon of 

 the human mind, going and coming like a planet, whose orbit 

 had not been calculated. Man}' able and ingenious minds 

 have been and are now working with wonderful enthusiasm 



