VI. TERRESTRIAL MAGNETISM. 249 



1150. Portable Magnetic Dip Circle, 3J in. needle, made 

 for, and used by, the late Sir John Shuckburgh. The dividing is 

 very fine, and believed to be Ramsden's. G. J. Symons. 



GENERAL. 



1176. Photograph of an Inclinatorium, by Daniel Ber- 

 noulli, completed by Johann Dietrich of Basle, in 1751. 



Professor Hagenbach-Bischojff, Director, The Physical 



Institute in the Bernoullianum, Basle. 

 This instrument gained the Prize of the Academy of Paris in 1743. 



1177. Dip Circle, for determining the magnetic inclination, 

 adapted to needles of various lengths. (Barrow, London.) 



H. Lloyd, Trinity College, Dublin. 



1178. Theodolite Magnetometer, 9-inch circle, and colli- 

 mator magnets. (Jones, London.) 



H. Lloyd, Trinity College, Dublin. 



1179. Dip Circle or inclination compass. James How fy Co. 



1180. Terrestrial Magnetism Magnetometer, new pat- 

 tern, constructed to determine the magnetic moment of a magnet, 

 and the direction and intensity of the magnetic force at a given 

 place. Elliott Brothers. 



The instrument consists of two distinct parts. For the observations of the 

 deflection magnet, the copper box screwed to the centre of azimuth is used ; 

 underneath tbis passes, through the centre, a divided metal bar with a vernier 

 carrying a magnet ; at right angles to this bar is the observing telescope. 

 The hollow vibration magnet, with a scale on glass at one end and a colli- 

 mating lens at the other, is observed through another telescope. The latter 

 magnet is suspended in the mahogany box above the copper box. 



1184. Declinatorium for sea and land observations. 



Carl Bamberg, Berlin. 



The instrument is furnished with gimbals for use at sea, and may be fixed 

 for observations on land. The magnetic system, which is provided with a 

 speculum, is constructed for reversal, and oscillates upon a point ; the ad- 

 justment is effected by means of a collimator telescope, and orientation from 

 terrestrial and astronomical objects. 



1185. Deviation Magnetometer, for determining the mag- 

 netic relations on iron vessels. Carl Bamberg, Berlin. 



The deviation magnetometer enables determinations of deviation (declination 

 and inclination) to be read off on points, and also determinations of horizontal 

 and vertical intensity by oscillations and deviations. A small telescope serves 

 for orientation by terrestrial and astronomical objects. The instrument may 

 be mounted on the same stand as the compasses. 



