LONDON. Royal Society,1 June 30.—C. Chree and J. M. Stagg: Recurrence phenomena in terrestrial magnetism. Making use of tho daily international character figures for 1906 to 1925 issued from De Bilt, an attempt is made to enlarge our knowledge of the 27-day interval in terrestrial magnetism. Assuming magnetic disturbance to be caused by some kind of electrical discharge from the sun, if sunapots were the sole or principal source of tho discharge, we should expect the interval to be longer in years of high than in years of low spot latitude. No recognisable difference is, however, found. In opposition to results obtained by Dr. Deslandres, no trace is found of periods which are submultiplos of 27 days. On the other hand, days which follow from 4 to 6 days after a very quiet day prove to have a greater than average chance of being highly disturbed days.