156 



OCEAN ATMOSPHERIC -ELECTRIC RESULTS 



destroying a small ion diminishes. For a quantitative 

 test of the average effectiveness of the nucleus in de- 

 stroying a small ion, the value of ou has been calculated. 

 The resulting values are tabulated in the last column of 

 table 3, each value being obtained through the applica- 

 tion of equation (4), using mean values of nuclei and 

 positive small-ion content of the air for each leg. The 

 values of o) are seen to vary from about 7to0.2xl0-6, 

 corresponding to the lowest and the highest nuclei con- 

 tent respectively of the air. It might be pointed out in 

 passing that a similar variation in the value of gj was 

 obtained by Torreson (7) from data obtained at the 

 Huancayo Magnetic Observatory. In that case, however, 

 there was a much greater spread in both the nuclei and 

 the small-ion content of the air. The variation in the 

 value of oj was explained by Torreson as due to a 

 change in size of the nucleus. 



The value of w calculated for the two legs, Balboa 

 to Easter Island and Easter Island to Callao, is much too 

 large if the value of 2 tji is taken as equal to 10 x 10-6 

 (3). A value of oj even as great as 5 x 10"^ would re- 

 quire that all nuclei be charged. The large values de- 

 duced for o) for these two legs may be the result of in- 

 correct values of nuclei content, as the nuclei counter 

 may not have been functioning properly during that part 

 of the cruise. The receiver of the instrument fell apart 

 from the pump during observations on December 18, a 

 few days after leaving Easter Island. Repairs were soon 

 made and observations continued for the remainder of 

 the leg. At Callao another instrument became available 

 and was used for all subsequent work. The measure- 

 ments with the second instrument gave noticeably higher 

 values than those with the original instrument, in the 

 ocean region near Callao. The mean of the first ten sets 

 after leaving Callao was 757, whereas the mean of the 

 last ten sets before arriving at Callao (made after De- 

 cember 18) was only 201. It seems probable that the 



original instrument was making too small a count not 

 only after December 18, but for some time previous to 

 this date, possibly as early as the beg:inning of Novem- 

 ber. If one eliminates the data between Balboa and Cal- 

 lao, thus eliminating the impossible values of cu , then 

 the mean nuclei content of the air for the entire cruise, 

 as shown in table 3 will be increased to 2000, while the 

 values of the positive and negative small-ion content of 

 the air will remain practically unchanged. This adjust- 

 ment would diminish the average values of oo for cruise 

 Vn (1.0 X 10-6) by 11 per cent, and the high values of oo 

 for legs 6 and 7 being thus omitted, the range in values 

 of CO for other legs of the cruise would be 2 to 0.2 x 

 10-6. 



The results on condensation nuclei and small-ion 

 content of the atmosphere over the oceans may be sum- 

 marized as follows: 



1 . The average nuclei content over the oceans (about 

 2000 per cc) is appreciably smaller than that for the land 

 stations where this element has been measured. 



2. There is no systematic diurnal variation in the 

 number of nuclei over the ocean, according to either 

 local or Greenwich time. 



3. The average nuclei content of the air spears to 

 be sufficiently great to reduce the average small-ion 

 content by about 44 per cent. 



4. The detailed relation between nuclei content and 

 the small-ion content of the air over the oceans found in 

 cruise VII measurements is accounted for, assuming 

 that the usually accepted equilibrium equation holds, 

 through a change in the efficiency with which a nucleus 

 combines with a small ion. A decrease in efficiency ac- 

 companies an increase in the nuclei content of the air. 



5. Calculations based on the equilibrium equations 

 indicate that, in the air over the oceans, there are on the 

 average, about 200 large ions of each sign per cc. 



LITERATURE CITED 



1. Wait, G. R. 1930-1931. The number of Aitken nuclei 



over the Atlantic and Pacific oceans as determined 

 aboard the Carnegie during 1928-1929. Carnegie 

 Inst. Wash. Year Book 30, p. 366. 



2. Nolan, J. J., R. K. Boylan, and G. P. deSachy. 1925. 



The equilibrium of ionization in the atmosphere. 

 Proc. R. Irish Acad., vol. 37, sec. A, pp. 1-12. 



Wait, G. R. 1931. Diurnal variation of concentration 

 of condensation-nuclei and of certain atmospheric- 

 electric elements. Terr. Mag., vol. 36, pp. 111-131. 



Gish, O. H. 1939. Terrestrial magnetism and elec- 

 tricity. Physics of the earth--VIII, pp. 183, 186. 



3. Harper, W. R. 1934. On the theory of the combina- 



tion coefficients for large ions and for uncharged 

 particles at any pressure. Phil. Mag., vol. 18, pp. 

 97-113; On the theory of the combination coefficients 

 for large ions: A correction. 1935, vol. 20, p. 740. 



4. Torreson, O. W. and G. R. Wait. 1934. Measurements 



of total nuclei, of uncharged nuclei, and of large ions 

 in the free atmosphere at Washington, D. C. Terr. 

 Mag., vol. 39, pp. 47-64. 

 Sherman, K. L. 1940. Total and uncharged nuclei at 

 Washington, D. C. Terr. Mag., vol. 45, pp. 191-204. 



5. Swann, W. F. G. 1917. Causes of atmospheric ioniza- 



tion over the ocean. Researches of the Department 

 of Terrestrial Magnetism, vol. 3, pp. 414-415. 



6. Wait, G. R. and O. W. Torreson. 1934. The large-ion 



and small-ion content of the atmosphere at Washing- 

 ton, D. C. Terr. Mag., vol. 39, pp. 111-119. 



7. Torreson, O. W. 1939. Condensation nuclei in the at- 



mosphere at Huancayo Magnetic Observatory, Huan- 

 cayo, Peru, and their relation to meteorological ob- 

 servations. Terr. Mag., vol. 44, pp. 59-74. 



