Licence: Public Domain Mark
Credit: The atmosphere in relation to human life and health. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![Tli(^ weij^lit of the deposit was at Kew 30 <;ram.s in I'O yards. At Chelsea the same area j^ave 40 j>;rams, which is ecjuivaleiit to 2^5 ])(nmds to the acre, or C tons to tlie scjuare mile. A large ])roi)ortioii of the deposits of fo^' in smoky towns clearly arises from the imperfect combustion of coal. On j)lants the deposit is sticky, like brown ])aint, and is not washed otfby water. A country fog is harndess in a green- house; a town fog most destructive, killing soft-wooded plants, and greatly damaging others. A very large number of plants will not thrive in smoky towns. In Manchester, the deposit colh^^ted from aucubii leaves gave C to 9 per cent of sulphuric, and 5 to 7 per cent of hydrochloric acid, mostly in a state of combination. Tiiree days' fog deposited per square mile li liundredweigLts of sul])huric acid and 13 hundredweights of blacks. Among the results of smoky air in towns may be mentioned: The discouragement of cleanliness and ventilation; the constant deficiency of light; the damage to plant life, so that only a few trees and plants can live; the destruction and disfigurement of stone, cement, iron, paint, wall papers, clothing, etc., and the depressing effect of dirt and bla(;kened streets on the peoi)le; losses to artists of all kinds who depend on light; the lowered vitality of a large portion of the poi)ula- tion, and a contributory influence toward the rapid degeneration and extinction of town families. In London the extra expenditure entailed is about £1 a head, or more than the value of all the coal burnt in houses. The extra wash- ing, painting, aud repairs, and the loss of unburned carbon, etc., are among the principal items in the account. The intensity of the ground fog depends largely on the amount of cooling which the earth has previously undergone. At the beginning of February, 1880, the ground in London was hard frozen with the intense frost which had i)revailed for some days. A moist southerly current supervened and the temperature rose several degrees above the freezing point. On the shady side of squares the fog then pro- duced between the ground and 10 or 20 feet above it was so dense that at 10 a. m. a lamp-post 4J yards distant was invisible. In an ordinary thick fog, such as that of January 11, 1888, objects are visible at thir- teen times that distance. Above the shallow stratum of ground fog the air was nearly clear aud the smoke escaped. Such fogs are due partly to radiation into space, but also lai*gely to the mixture of the warm current with air which has become cold by contact with the ground, and to radiation toward the ground. All radiation fogs disperse or greatly diminish when the sky becomes clouded and reflects some of the warmth radiated from the ground. They are not formed under a cloud}- sky. 2. Fog is frequently produced, sometimes ou an euormous scale, cov- ering an area exceeding that of the British Isles, by the mixture of opposite currents of small velocity. The condition of atmosphere often](https://iiif.wellcomecollection.org/image/b21208724_0047.jp2/full/800%2C/0/default.jpg)
