

VI. TERRESTRIAL MAGNETISM. 291 



1191. Portable Unifilar Magnetometer. An instrument 

 for determining the horizontal intensity of terrestrial magnetic 

 force ; and also the declination. 



Keic Committee of the Royal Society. 



It consists of two parts : one for determining the time of vibration of a 

 suspended magnet ; the other for determining the amount of deflection it pro- 

 duces when caused to act upon a second needle. 



In addition there is a third magnet, which is subsequently suspended, 

 and its position referred to the astronomical meridian, by means of a 

 mirror, which serves to allow of an observation of the sun's azimuth being 

 made. 



Used by the Rev. S. J. Perry, F.B.S., during the late Transit of Venus 

 Expedition to Kerguelen. 



1192. 12-inch Dipping Needle. Royal Society. 

 1192a. 12-inch Variation Needle. Royal Society. 



1193. Kew Pattern Dip Circle. 



Kew Committee of the Royal Society. 



Dip circle of the pattern adopted by the Kew Observatory, having needles 

 3 ins. long, which are read by microscopes, carried by a circle in front of the 

 needle frame. It is also provided with accessory needles, for determining 

 total force, after the method of Dr. Lloyd. 



1196. Portable Theodolite for the observation of the Mag- 

 netism of the Earth, constructed by Dr. Meyerstein, Gottingen. 



Prof. Dr. A. Kundt, Strasburg. 



1197. Edelmann's Telescope with graduated Scale, 



for reading reflecting instruments (small). 



M. Th. Edelmann, Munich 



1198. Edelmann's Telescope with graduated Scale, 



for reading reflecting instruments (large). 



M. Th. Edelmann, Munich. 



1199. Edelmann's Telescope with graduated Scale, 



for two observers. M. Th. Edelmann, Munich. 



1200. Edelmann's Rider, for observing two objects at the 

 same time by means of a telescope with graduated scale. 



M. Th. Edelmann, Munich. 



1201. Edelmann's Declination Magnetometer. 



M. Th. Edelmann, Munich. 



1202. Edelmann's Variation Instrument for Declina- 

 tion. M. Th. Edelmann, Munich. 



1203. Edelmann's Variation Instrument for Horizontal 

 Intensity. M. Th. Edelmann, Munich. 



T 2 



