Periods and Logarithmic Decrement of the Gravitation Needle under High Exhaustion.

The values of the radiation potentials for strontium and barium have not been directly determined, but Mohler, Foote and Megers (Sci. Paper, Bureau of Standards, No. 403, 1920) give estimates from the wave-lengths of the tail lines of the proper spectral series for these elements. Hydrogen is added to the table, although not given by Eve. An inspection of the table brings out the following: For Group I, the degree of constancy of the products is nearly the same, being slightly in favor of the use of I rather than (I R). Group II A, shows, on the other hand, that (I R) gives a better agreement than I. This is still more marked in Group II B. Group V A is considerably more favorable to (I R). In case of the inert gases the product using I alone does not hold at all, while the product (I R) gives nearly a constant. The product using (I R) places hydrogen in good agreement with the first Group. Mercury, which has some of the physical qualities of the inert gases, has a product about equal to that for those gases. In case of the whole table, going from Group to Group, the products using (I R) are much more constant than is the case with I alone.