The Coronal Method of Estimating Atmospheric Nucleation
I. Introductory. -With the advent of spring the values of atmospheric nucleation, if laid off on the same scale as in my earlier papers, have returned to the low order of values found last fall and the details of the temperature effect are obscured. I have supposed from this that temperatures below freezing are particularly favorable to high nucleation. One may note, moreover, that the distribution of atmospheric electrical potential is a maximum in winter and falls off in its yearly period in
... s yearly period in a way similar to the observed nucleation. The frequent occurrence of day minima in both cases should also be noticed. The presence of maximum nucleation during the winter months when the maximum of dust contents is certainly to be anticipated for the summer, together with the fact that the numbers of nuclei found by the coronal method is much lower than the usual order of Aitken's 1 data, is worthy of remark. To produce coronas the nuclei must be very closely of the same size ; for in a large trough, a rigorous uniformity of diameter of fog particle and possibly of distribution is implied, if the corona produced is to be sharp and brilliant. Particles of even slightly different sizes would give a blurred effect or a mere fog. Hence, as I understand it, the effect of ordinary dust vanishes from the corona and the nucleation observed is probably something much more definite. It is for this reason that in spite of very discouraging drawbacks, my interest in the subject has not waned, though I am well aware that the effect of chemical products of combustion in winter, such as sulphuric acid and the sulphides, has not been eliminated. The subject as a whole has received enhanced interest in view of its relation to Arrhenius's interpretation of the geophysical impor-1 In the country after rain, 32,000 ; clear, 130,000 ; in cities, 100,000 to 500,000, etc. These data are about five times larger than the coronal values.