of Terrestrial Magiietism. 51 



are the magnetic stations that merit preference at the present 

 time, or that local circumstances may admit of establishing. 

 To have solicited the concurrence of the Royal Society of 

 LfOndon will be sufficient to give new life to a useful enter- 

 prise in which I have been engaged for very many years. I 

 venture simply to express the wish that, should my proposi- 

 tion be received with indulgence, the Royal Society would 

 enter into direct communication with the Royal Society of 

 Gottingen, the Royal Institute of France, and the Imperial 

 Academy of Russia, in order to adopt measures the best 

 adapted for the combination of what it may be proposed to 

 establish with what already exists upon a very considerable 

 extent of surface. Perhaps also measures might be previously 

 concerted for the publication of i:)artial observations, and also 

 (if the calculation would not i-equire too much time, and too 

 much retard the communications,) of the mean results. Oneot 

 the happy effects of civilization and the progress of reason is, 

 that when addressing learned societies, their willing concur- 

 rence may be relied upon if the object for which it is solicited 

 tends to promote the advancement of the sciences or the intel- 

 lectual development of humanity. 



Labours of astonishing precision have been performed, 

 within the last few years, with instruments of extraordinary 

 power, in a magnetic pavilion of the Observatory of Gottin- 

 gen, which are well worthy of the attention of philosophers, 

 as they offer a more precise method of measuring the horary 

 variations. The magnetized bar is of much larger dimensions 

 than even the bar of Prony's magnetic telescope ; and the ex- 

 tremity is furnished with a mirror, in which are reflected the 

 divisions of a scale which is more or less distant, according to 

 the angular value desired to be given to these divisions. By 

 the employment of this improved method the necessity for the 

 observer's approaching the magnetized bar is obviated, and 

 by preventing the currents of air produced by the proximity 

 of the human body, or dui'ing the night, of a lamp, observa- 

 tions may be made in the smallest intervals of time. The 

 great geometrician Mr. Gauss, — to whom we ov/e this mode of 

 making observations, as well as the means of reducing the in- 

 tensity of the magnetic force in any part of the earth to an 

 absolute projiortion, and the ingenious invention of a magneto- 

 vietcr put into motion by a multiplier of imhiction, — pub- 

 lished in the years 1831- and 1835 several series of simulta- 

 neous observations made with similar apparatus, and at inter- 

 vals of five or ten minutes, at Giittingen, Copenhagen, Altona, 

 Brunswick, Leipzig, Berlin (where Mr. Encke has already 

 established a very spacious magnetic house, near the New 

 Royal Observatory), Milan, and Rome. Mr. Schumacher's 



H2 



