Show WHAT FOGS ARE MADE OF nebula and their airy relative Eela tive of town and country A convenient though not strictly scientific classification of fog types is sea or coast fog valley or hill fog and town or dust fog the last named has been given the euphonic designation nebula pul verea it is an artificial rather than a natural condition the bev clement ley who gave a large portion of his life to cloud study says in ins book cloudland Olo udland that in some parts of the globe nebula pul verea is occasionally so thick as to obscure almost totally the sunlight and in abyssinia has led to the tradition that the or darkness in egypt was in reality an unusual dust fog the amount of moisture varies so much in different fogs that the terms dry and wet are used the scientific name of the latter being nebula stil lans in wet fog the particles are apt to be larger than in dry fog A still further division due we believe to robert H scott is log or fog in which no rain falls while the temperature generally low in the morning continues to rise during the day and cyclonic fog in which rain does occur while the temperature remains about temporary before leaving these town fogs wo may notice the part played by them in affecting the health of the community mr scott has given figures showing the mortality from diseases of tho respiratory system for some of the more memorable fogs of london we have room for but one of the many periods he gives from jan 26 to feb 6 1 london days average temperature ar y in iho morning was 26 degrees F the total death rate was per 1000 a rate unequaled since the last cholera epidemic and there were no less than 1557 deaths from diseases of the respiratory organs it is not always an easy matter to trace direct relationship even where tho statistics are carefully gathered but there can be little doubt that these town fogs are unwholesome indirectly they affect the health of tho community in a way few would imagine A town fog is on excellent trap for noxious gases holding them close to the ground dr R bames studying this question found by inspection of gas plants near london that in foggy weather tho escaping gas was held in concentrated form in and near tho borla there are other sources of contamination in foul emanations from the ground sewers etc on clear bright days even if no wind is blowing the law of diffusion of gases acts more effectively and helps disperse the gases harpers |