406 Dr. Trask on the Aurora of 1859. 
to address to the Academy. I enumerate the principal points 
observed. ist. There was no noise in the aurora. 2d. The 
freely suspended needle of Marianini’s Ré-Electrometer mani- 
fested not the slightest oscillation. 38d. The gold leaf electro- 
9. Observation at San Francisco, California; by Dr. JOHN 
Trask. (In a letter to the Editors, dated Sept. 1st, 1859.) 
On the night of the 28th of August, at the hour of 10 o'clock, 
and continuing from that hour until near daylight we had for 
the first time in ten years in California a fine display of the 
Aurora. The sky was illuminated from the northwest to the 
northeast, with a flood of crimson light extending to the zenith, 
through which the whiter and yellow columns would start at 
varied intervals. It was a magnificent display and will compare 
favorably with the best varieties of your wintry months. 
10. Height of the base of the Auroral curtain, Aug. 28. 
The minimum altitude above the southern horizon of the 
lower margin of the meridional part of the auroral curtain, seen 
during the display of Aug. 28th, previous to 9 P. ., was de- 
termined independently by Prof. C. S. Lyman and by Mr. E. C. 
Herrick at New Haven, and by Prof. A. ©. Twining at West 
Point, N.Y. These three determinations were made at about 
