276 FOG AND CLOUDS, GENESIS OF. 



FORSTER, WILLIAM E. 



of breaking up matter very minutely can con- 

 tribute a share. The spray from the ocean is 

 probably an important source. Meteoric mat- 

 ter, it is likely, furnishes a considerable pro- 

 portion. The process of combustion produces 

 copious quantities of very finely divided mat- 

 ter. If there is an excessive quantity of these 

 particles in the air, they remain floating with a 

 film of water condensed upon each of them, 

 giving rise to the dense but light form of con- 

 densation called fog. This explains the preva- 

 lence of fogs in large cities and in factory dis- 

 tricts. The experiments made by Aitken showed 

 that simply heating a substance, for example 

 glass, iron, or brass, gives rise to a cloud of 

 dust of this nature. By collecting the air in 

 which bodies had thus been heated into a re- 

 ceiver, he obtained a very dense mist by the 

 injection of steam. A particle of iron weigh- 

 ing only T 7 grain when heated in pure air 

 gave off enough dust to cause a distinct misti- 

 ness. An experiment was tried with combus- 

 tible gas and air, both thoroughly filtered. 

 Their combustion in the receiver gave rise to 

 an atmosphere in which an exceedingly thick 

 mist was formed by the admission of steam. 

 When purified air and ordinary air were 

 compressed successively by an :iir-pump with 

 a little water to produce saturation, upon re- 

 moving the pressure a foggy appearance was 

 presented by the common air, but no change 

 was visible in the filtered air. When air con- 

 taining a small quantity of dust was placed in 

 the receivers the cloud-particles were heavy 

 and fell to the bottom like fine rain ; but when 

 there was much dust a permanent white mist 

 formed. Experiments with different substances 

 with the view of finding out their capacity for 

 emitting dust showed common salt when burned 

 in a fire, or in the flame of a spirit-lamp, to be 

 one of the most active fog-generators. The 

 air of the laboratory in which gas was burning 

 gave a much denser fog than the air outside, 

 and no difference could be detected in the 

 density of the fog produced by burning gas 

 with a bright or a smoky flame. The products 

 of a perfect combustion and of a smoky com- 

 bustion of fuel in a fire were also compared, 

 without any difference in their fog-producing 

 qualities being noticeable, while both were 

 much more active than other air. Sulphur 

 when burned gave rise to the most dense fog 

 given by any substance, it being impossible to 

 see through a thickness of five centimetres of 

 the atmosphere thus produced. The vapors of 

 other substances, such as sulphuric acid, alco- 

 hol, benzole, and paraffine, acted in the same 

 manner as watery vapor, condensing in a dust- 

 laden atmosphere but remaining perfectly clear 

 in filtered air. The fogs of London and other 

 large cities would not be averted by more per- 

 fect combustion of fuel, but would only be ren- 

 dered whiter and purer. The quantity of sul- 

 phur burned in the coal in London is estimated 

 to amount to 200 tons a day in winter. This 

 would account for the density of the London 



fogs. The sulphur may serve a good purpose 

 as a disinfectant and deodorizer, as the air dur- 

 ing a fog is perfectly stagnant, and is probably 

 full of the germs of disease, which would more 

 frequently cause infection were it not for the 

 antiseptic action of the sulphur, and also of the 

 smoke-particles with which the fogs of London 

 and such cities are filled, and which make them 

 so much more disagreeable. Smoke descends 

 during a fog because the particles of soot are 

 good radiators which soon cool, and then form 

 nuclei on which the water-vapor condenses 

 more readily than on the other dust-particles, 

 by which they become heavier cind fall. This 

 is the reason why the phenomenon of falling 

 smoke, caused by a saturated condition of the 

 atmosphere, often indicates the approach of 

 rain. Experiments with rain-drops have been 

 made by Professor Lister, who found that they 

 produced great numbers of living organisms in 

 sensitive solutions. It is therefore probable 

 that the germs of disease and putrefaction 

 form a part of the fog-generating dust. 



FOOTE, HENRY S., was born in Fauquier 

 County, Virginia, in September, 1800. Having 

 graduated at Washington College, Lexington, 

 he removed first to Tuscumbia, Alabama, where 

 he practiced law and edited a Democratic news- 

 paper, and then to Jackson, Mississippi. He 

 was elected to the United States Senate in 

 1847. In 1848 he was chairman of the Com- 

 mittee of Foreign Relations. In 1850 he ad- 

 vocated the compromise measures. In 1851 

 he became the Union candidate for Governor 

 of Mississippi. General J. A. Quitman was his 

 opponent, but a short time before the election 

 his defeat became evident, so that he with- 

 drew, and Jefferson Davis was substituted for 

 General Quitman. Foote was elected. At the 

 close of his governorship he moved to Cali- 

 fornia. In 1858 he returned and resided at 

 Vicksburg. He was a member of the Knox- 

 ville Convention, strongly opposed to disunion, 

 yet he took the Southern side at the outbreak 

 of the war. He was a member of the Con- 

 federate Congress, and was a thorn in the 

 side of his compatriots. Finally, he left Rich- 

 mond and went to Washington. Mr. Foote 

 was irascible in temperament. He had a per- 

 sonal encounter on the floor of the United 

 States Senate-Chamber with Thomas II. Ben- 

 ton, when they were both Senators. He was 

 involved in several duels, one with Winston, of 

 Alabama, another with Sargent S. Prentiss, 

 and a third with Claiborne, of Mississippi. He 

 was a firm believer in the "code of honor,' 1 

 but a wretched shot, so that his various affain 

 were bloodless. Mr. Foote filled the post oi 

 Superintendent of the United States Mint in 

 New Orleans in later years. His health in^ 

 duced him to return to his home in the neigh- 

 borhood of Nashville, Tennessee, where he 

 died May 20th, in the eightieth year of his 

 age. 



FORSTER, WILLIAM EDWARD, the Chief Sec- 

 retary for Ireland in the new English Cabinet of 



