. Journal. e negatively chargedtowards the positive electrode, neutral particlesbeing unaffected. Tobacco smoke examined in thisway shows a mixture of positively and negativelycharged particles with some which are neutral. In order to examine this effect a simple apparatushas been devised which consists of a vulcanite cell,2 or 3 mm. deep and about 1 cm. in diameter, whichcontains two insulated electrodes connected toterminals on the outside. The cell can be placedupon a microscope slide and closed above bya cover-glass. Such a cell illuminated by the dark-ground method, and examined under a c
. Journal. e negatively chargedtowards the positive electrode, neutral particlesbeing unaffected. Tobacco smoke examined in thisway shows a mixture of positively and negativelycharged particles with some which are neutral. In order to examine this effect a simple apparatushas been devised which consists of a vulcanite cell,2 or 3 mm. deep and about 1 cm. in diameter, whichcontains two insulated electrodes connected toterminals on the outside. The cell can be placedupon a microscope slide and closed above bya cover-glass. Such a cell illuminated by the dark-ground method, and examined under a compara-tively low power, say a ? in. objective and xlO eye-piece, shows the particles of tobacco smoke sus-pended in the air between the electrodes, eachparticle in rapid Brownian movement. By charg-ing the electrodes the movements of the particlescan be examined. The cell is illustrated in Fig. I,and it is hoped that by its use it may be possible toascertain the electrical condition of London Fig. 1 Soikces of Dust The common sources of dust are the smoke fromimperfect combustion and dust blown up from theground. There are other sources whose importancehas not yet been ascertained ; the most probable seemto be volcanic, cosmic, and solar. It is well knownthat the finer particles of dust ejected during vol-canic eruptions may remain in suspension in the airfor many month-; again, the arrival of dust fromoutside the earths atmosphere, either of cosmic orBolai origin, would tend to bring about a concen-tration in the lower strata of the air, since the rateof settlement of such particles through the airwould be continually reduced owing to the increas-ing density of the air near the earth. An extractfrom the Barbados Advocate of May 23, 1922, wasreferred to in the Meteorological Magazine of July last. This is of great importance in the presentconnexion and reads as follows:—A peculiarphenomenon which has spread over the wholeCarribbean from Barbados to St. Kitts,
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectchemist, bookyear1882
