Magnetic Observations at Cambridge, United States. 139 
A Brief Abstract of the Observatory Records, giving some Account 
of the most conspicuous Auroras, and other Meteorological Phenome- 
na that have been noticed and registered at Cambridge, during the 
Period embraced by the Magnetic Observations. 
[The time is mean solar astronomical for Gottingen. ] 
November 18, 1841. —13h. 44m. At this time a very beautiful 
Aurora was seen. The period of greatest brightness was 13h. 25m. 
The Horizontal-Force Magnetometer was then vibrating rapidly, and 
at 13h. 44m. it moved over ten divisions of the scale (201-212), 
but its disturbed movements gradually died away. At 13h. 50m. 
the Aurora had nearly vanished, leaving only faint traces of columns. 
The Declination-Magnetometer had its ordinary slow motion. 
The readings of the Horizontal-Force Magnetometer, for a short 
time, commencing at 13h. 47m. 30s., were: 
200.5 196.0 195.8 204.0 
204.0 202.0 200.5 201.6 
198.0 197.3 195.8 205.8 
204.0 201.0 1h.56m. 205.0 202.0 
199.0 196.3 199.0 205.0 
200.5 201.3 
At 14h. 30m. there was observed in the north a large, bright 
arch of light, moving slowly westward, and also small, drifting 
spots of bright light near the horizon. At 14h. 40m. the illumi- 
nation extended from the northern horizon up to 30° of altitude. 
At 17h. the Aurora was shining brightly again. 
December 24, 1841. — At 12h. delicate shoots of Aurora nearly 
up to the zenith were visible. At 12h. 10m. the Aurora disap- 
peared near Capella, but grew brighter in the zenith. At 12h. 
12m. it disappeared from the zenith, and shone again in Auriga. 
At 12h. 16m. no trace of the Aurora could be seen; the Mag- 
netometers swung over fifteen divisions of the scale. At 12h. 21m. 
the Aurora was invisible. The declination stood at 144.8; the 
Horizontal Force read 149 - 158. 
January 4, 1842. — From Ih. 45m. to 12h. 15m. an Aurora was 
seen in the northeast and northwest. The Magnetometers were 
stationary, except in the interval from 12h. 2m. to 12h. 8m., when 
the Declination changed from 140.8 to 143.2, and the Horizontal- 
