THE 

 LONDON, EDINBURGH and DUBLIN 



rHILOSOPHIOAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



MARCH 1854. 



XXIII. Reports on the Progress of the Physical Sciences. 

 By Dr. Hirst. 



On the Application of Magnetic Induction to tJie determination of 

 the Magnetic Inclination. By Prof. \V. Weber. 



[Poggendorff's Annalen, vol. xc. p. 209.] 

 [With a Plate.] 



IT is known that by the investigations of Gauss, observations on 

 terresti'ial magnetism have been raised from mere compari- 

 sons to actual measurements, which in point of precision are 

 comparable to astronomical ones. The system of measurement 

 here referred to has, however, been employed hitherto in obser- 

 vations on the horizontal elements of the earth's magnetism alone, 

 the horizontal intensity and declination. It is true that these 

 horizontal elements form in themselves a complete system, from 

 which, as Gauss has shown, a complete determination of the 

 earth's magnetism may be obtained without the aid of observa- 

 tions on the inclination. But it is also true that the attainment 

 of this end would be facilitated by means of observations on the 

 inclination, and hence the latter must not be disregarded. At 

 ])rescnt, however, such observations by no means possess that 

 classic character which those on the horizontal elements have 

 attained through the use of the magnetometer. The causes 

 of their deficiency in this respect arc essentially two : First. 

 The action of the vertical magnetic force is not observed by 

 itself, but in combination with the action of gravity on our i)on- 

 dcrable needles. A separation of the effects due to each of the 

 two forces is certainly possible, by demagnetizing the needle 

 and thus obtaining several combinations of the two; but the 

 Phil. Mag. S. 4. Vol. 7. No. 44. March 1854. M 



