11 



and two ante-rooms to the south, with the lobby and entrance doors 

 between. 



The magnetometers and telescopes in the observatory are placed on 

 stone pillars of about 20 inches diameter, having good foundations, 

 and being completely disconnected with the floor, so that no tremor 

 can be communicated to the instruments by walking past them. 



The instruments in the observatory are of two classes, Magnet- 

 ical and Meteorological. 



Belonging to the former class, there are, 1 . The Declination 

 Magnetometer, used for determining the variations and absolute 

 values of the angle formed by the astronomical and magnetic meri- 

 dians. 2. The Bifilar Magnetometer, by means of which the varia- 

 tions of the horizontal component of the earth's magnetic force are 

 obtained. 3. The Balance Magnetometer, which gives the varia- 

 tions of tlie vertical component. 4, The Inclinometer, used for ob- 

 taining the magnetic dip, or the angle formed by the direction of the 

 earth's total intensity, and a horizontal plane, namely, m the mag- 

 netic meridian. 5. An extra Declinometer in a small wooden build- 

 ing, at a distance from the observatory, is used for obtaining the 

 absolute value of the horizontal component of the earth's magnetic 

 force, according to the method of Gauss. 



The second class of instruments is the Meteorological. 



These are, — 1, The Barometer, a standard by Newman, similar to 

 that belonging to the Royal Society. The tube is 0'552 inches in 

 diameter. 



2. Thermometers. The dry and wet bulb thermometers, by Messrs 

 Adie and Son, are placed on a revolving wooden frame opposite one 

 of the north windows. They are always read from within the 

 observatory, the frame being moved by means of cords and puUies. 

 Maximum and minimum register thermometers, by Adie and Son, are 

 placed on the north side of the observatory. Self-registering black 

 bulb thermometers, for solar and ten-estrial radiation, are placed in 

 an enclosed space at a distance from the observatory. 



3. Anemoscope and Anemometer. 



4. The Rain-Gauge. 



In 1841 and 1842, daily observations were made at the Gottin- 

 gen hours of 8 and 11 a.m., and 2 and 5 p.m. ; in 1843 at 6, 8, 

 10, A.M. ; Noon ; 2, 4, 6, 8, and 10, p.m. Another observation was 

 made at 11 a.m., after October 1843; in 1844, at every hour of 

 the twenty-four; and this system is being continued in 1845. 



The instruments observed at these hours were, the declination, the 



