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OF THE NATIONAL ACADEMY OF SCIENCES Volume 7 MAY 15, 1921 Number 5 THE DIFFUSION OF AIR THROUGH WATER IN THE LAPSE OF YEARS1 BY CARL BARUS Department OF PHYSICS, BROWN UNIVERSITY Communicated January 10, 1921 In 1912 I put up a U-tube of the form annexed, containing a charge of water, ww', below the air chambers, aa', both at nearly atmospheric pressure. The tubes were sealed by fusion cautiously, to avoid the presence of flame faces in aa'. They were then put away in a dark vault of nearly constant temperature, for short time ranges, to be examined from time to time as to the displacement of the thread of water within: for it will be seen that the meniscus under a' is at a pressure excess of hpg as compared with the meniscus under a. If L is the total length of the thread of liquid in the tube, we may define the coefficient (k) of diffusion (by volume) by the equation v = Kat(hpg)/L where v is the volume diffusing at nearly constant mean pressure in the time t through an area a, the density of liquid being p = 1. K = Hence, where dh/dt is the loss of head per second. The factor 1⁄2 appears since the volume lost at a' appears at a, and their sum is equivalent to the loss of head. The amount of diffusion is so small that corrections may be disregarded. The observations made before the spring of 1914 were not satisfactory because of deficiencies of method. They were, therefore, discarded. Measurement was thereafter made with the cath etometer. The following table gives the essential data for the interval of 6 years, 9 months and 6 days with the increment from leap years: The two values of κ found are of the same order, but the one for tube II is definitely larger than the one for tube I. This may be due to infinitesimal difference in the separated gases (a,a') of the tubes. But since the tube II has a shorter (L) and wider column, and a meniscus nearer the bend, it is more probable that thermal correction is the cause of the difference; for the inside sectional area of II is about 2.2 times larger than that of I. The data obtained for « with a cylindrical cartesian diver (Carnegie Publications, No. 186, Washington, 1913, p. 21) about 3 cm. in diameter of 7.05 cm2. in area, are enormously larger than the above, reading a = 90 X 10-12. The result is in keeping with the enormously larger area and consequent effectiveness of the solution-temperature mechanism which I have described in the preceding paper. Whether in case of tube I, a condition of true diffusion has been reached will have to be ascertained in the lapse of further years. Meanwhile the question whether a long slender cartesian diver may not obviate the discrepancies hitherto encountered is worth consideration. 1 Advance note from a Report to the Carnegie Institution, Washington, D. C. 2 These PROCEEDINGS, 6, 1920 (495–8). THE INFLUENCE OF AGE ON FERTILITY IN SWINE1 BY TAGE ELLINGER COPENHAGEN, DENMARK Communicated by R. Pearl, March 10, 1921 In the breeding of domestic animals the problem of fertility is of prime importance. The neglect of this essential factor has again and again caused breeders disappointments and often heavy economic losses. Thus it is desirable to study this chapter of the physiology of reproduction thoroughly and to examine the factors, internal and external, that affect the ability to produce offspring. During an investigation on these subjects, in this laboratory the results of which are soon to be published, the writer has been confronted |