370 



SCIENTIFIC NEWS. 



but they observed the dip, and the number of oscillations 

 made in a given time by a horizontal needle, whence by a 

 very simple formula they deduced the number of oscillations 

 it would have made in its true direction, and the intensity of 

 - the magnetic forces. 



These did not To exhibit the whole of their labour at one view, and the 

 coincide with consequences deducible from it, Mr. Gay-Lussac has given 

 sis. a general table of the observations themselves, the geogra- 



phical latitude and longitude of the place, the latitudes and 

 longitudes referred to the magnetic equator according to the 

 hypothesis of Mr. Biot, the dips calculated according to 

 this hypothesis, and the differences they found between their 

 observations and this calculation. To this he has added ob- 

 servations on the nature of the soil, and its elevation above 

 the level of the sea. 

 The dips were it is to be remarked, that all these differences arc in the 

 same direction, the dips by calculation being from 3° 42' 

 to 5 Q 9' too great. Admitting, that some of these differ- 

 ences may be ascribed to local circumstances, or the un- 

 avoidable errours of observation, it appears at least highly 

 probable, that a more considerable part arises from the si- 

 tuation attributed to the nodes of the magnetic equator, and 

 to the angle it makes with that of the earth. It will not be 

 difficult to determine the corrections, that Mr. Biot's hy- 

 pothesis requires, to agree much better with these new ob- 

 servations, 'and reconcile them with those from which he 

 determined his first elements. It is to be presumed, that 

 Mr. Biot himself will consider this as an object of sufficient 

 importance to engage his attention, when he has finished the 

 important and difficult undertaking, on which he is now 

 employed*. To give this theory all the precision of which 

 it is susceptible, it is much to be wished, that we had a se- 

 ries of observations made in remoter parts of the globe with 

 the same care as those of von Humboldt and Gay-Lussac: 

 but in the mean time we perceive, that the intensity of the 



Meridian line * Messrs. Biot and Arago set off in September last to continue 

 r extended to the fa e meridian line to the Balearic islands, and finish the labours 

 a eanc is- interrupted by the death of Mr. Mechain. In December they be- 

 gan the observation of the great triangle, which is to connect the 

 island of Ivica with the coast of Valencia. 



magnetic. 



