The Senate Of The United
Published: 2013-09
Total Pages: 26
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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1845 edition. Excerpt: ...36.2 30.3 30.7 25.7 34.4 36.5 37.6 MAGNETIC OBSERVATORY AT I'll I: GIRARD COLLEGE, PHILADELPHIA. TERM DAY MAGNETIC OBSERVATIONS, FROM JUNE TO DECEMBER, 1840. GENERAL NOTES. The instrumente are thotc previously described in the notes pretixed to ordinary observations. Observations upon term days were commenced in 1839 with the declinometer only. On the term day of May, 1840, all the instrument were mounted, but the vertical force was not permanently adjusted. A remarkable aurora occurred, and, simultaneously, a great magnetic disturbance-I have therefore inserted the record of the observations, though, in reference to the vertical force, the value of the differences on the scale was not ascertained. The observations of the force instruments are uncorrected for temperature. In a subsidiary building. Augmented value of one division, 0'.345. Increasing readings correspond to decreasing declination. 10 P. M. Gottingen time, civil reckoning. f 1 minute 1 second too slow. The disturbance having carried the needle out of the field, the sensibility of the instrument was diminished by lowering the centre of gravity. As the twilight tailed an aurora became visible. In the course of the display, there were moving pillars, flashes from a low segment of light in the north, and a beautiful arch nearly or quite at right angles to the magnetic meridian. Pillars of aurora from 9A. 18m. to WA. 2m., varying in brightness and position;low segment of light to north, continued throughout the appearances; 10A. 5m., an arch forms from east to west; streamer of light, varying in brightness, fading and reappearing from 10A. 20m. to about IIA. 10m.; the brightest flashes at Uh. 6m. See general notes. Not.--The declinometer is a...