. Carnegie Institution of Washington publication. 48 NUCLEATION OF THE UNCONTAMINATED ATMOSPHERE. 42. Fog chambers—Filters with saturator.—The long rectangular fog chamber (Chapter II, section 16) of capacity ^=13,000 cc., having the volume ratio v \V^ = to the volume V of the vacuum chamber, was largely used. It is often difficult, however, to keep plate-glass windows perfectly tight. Hence the cylindrical fog chamber (length 45 cm., diameter 12 cm.) was substituted for it, in which case vIV Both the former and the latter were often incased in sheet lead, cm. thick, leaving m
. Carnegie Institution of Washington publication. 48 NUCLEATION OF THE UNCONTAMINATED ATMOSPHERE. 42. Fog chambers—Filters with saturator.—The long rectangular fog chamber (Chapter II, section 16) of capacity ^=13,000 cc., having the volume ratio v \V^ = to the volume V of the vacuum chamber, was largely used. It is often difficult, however, to keep plate-glass windows perfectly tight. Hence the cylindrical fog chamber (length 45 cm., diameter 12 cm.) was substituted for it, in which case vIV Both the former and the latter were often incased in sheet lead, cm. thick, leaving merely an open strip in the broad- sides for observation of the coronas. T A FIG. 40.—Filter with wet-sponge tube (saturator). In view of the difficulties encountered in the preceding chapter, the attempt was finally made to counteract the effect of periodicity by saturating the filtered air with water vapor before introducing it into the fog chamber. To do this the U tube, figure 40, filled with pieces of wet sponge was added to the filter F, the filtered air from B entering the fog chamber very slowly by way of the stopcock C. This innova- tion seemed at first to be remarkably successful, as the results of table 29 on page 50 will show. L,ater, however, there was a very definite recurrence of periodicity, the true cause of which I ultimately traced to the inevitable formation of water nuclei. In addition to the filter mentioned, an ordinary dry-cotton filter and a Pasteur filter were often used; but the latter was soon discarded, as it gave no additional free- dom from dust and prolonged the time of filtration inordinately. fl-F A P •w. FIG. 41.—Rectangular wood fog chamber A, with screening lead plates P and X-ray bulb B, exhaust pipe E, and filter pipe F. FIG. 42.—Cylindrical glass fog chamber A, with lead case L and bulb B. E is the exhaust pipe, F the filter pipe, p the plug for cleaning, and zc> the Please note that these images are extracted from
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