Abstract
The numbers in the table are based on observations made at the Zürich Observatory, supplemented by series furnished by 40 other observatories for the 68 days (indicated by asterisks) on which no observations were made at Zürich. The small increase of only 5.1 over the mean for 1926 (63.9) shows that we are nearing a sunspot maximum and, indeed, a rather low one.Figure 1 is a detailed graphical representation of the daily relative sunspot‐numbers for 1927 in which the times are plotted as abscissas, and the relative numbers, taken from the table, as ordinates. The limits of the successive solar rotations are indicated by vertical arrows in the upper edge of the figure. The secondary maxima and minima succeeding the rotation periods do not represent real fluctuations in sunspot‐activity but are rather to be attributed to the influence of solar rotation, and moreover, to a certain stability of centers of activity for spots and the special distribution of these centers in the direction of rotation.
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