The magnetic storm of August 11–12, 1919, as observed at the Apia Magnetic Observatory, Samoa

[From a blue print transmitted to the Journal by Dr. G. Angenheister, the observer‐in‐charge, the following information has been obtained respecting the chief characteristics of the severe magnetic storm of August 11–12—the severest registered at the Apia Magnetic Observatory since the one of September 26, 1909. All the times given refer to Greenwich civil mean time; they are to be regarded as approximate, as also the absolute value of the magnetic elements; the scalings were made by the Department of Terrestrial Magnetism.] Declination ( D ). No large perturbations occurred and there was no marked “sudden commencement” near 7 h August 11. At about 7 h 58 m , there is a sharp rise of a few minutes, signifying diminishing east declination ( D ); the value of D at this point is about 10° 14′ E. A minimum D of about 10° 02′ E is reached at about 9 h 53 m August 11. The total range in D for August 11–12 is thus about 12′.