MAGNETIC OBSERVATIONS. 115 



the torrid valley, elevation of the bottom of the valley 8153 

 feet, inclination 16. 02. (All the above-named inclinations 

 have been expressed in decimal parts of a degree.) 



It might perhaps be deemed unnecessary, considering the 

 extent of the relative distances and the influence of the 

 neighbouring kinds of rock, 44 for me to enter fully into the 

 details of the following observations : the Hospice of St. 

 Gotthard, 7087 feet, inclination 66 12' ; compared with 

 Airolo, elevation 3727 feet, inclination 66 54', and Altorf, 

 inclination 66 55' ; or to notice the apparently contradictory 

 data yielded by Lans le Bourg, inclination 66 9', the Hospice 

 of Mont Cenis, 6676 feet, inclination 66 22', and Turin 754 

 feet, inclination 6 6 3'; or by Maples, Portici and the margin of 

 the crater of Vesuvius; or by the summit of the Great Mili- 

 schauer (Phonolith) inclination 67 53'.5, Teplitz inclination 

 67 19'. 5, and Prague inclination GG^iT'.e. 44 Simultaneously 

 with the series of admirable comparative observations pub- 

 lished with the fullest details of the horizontal intensity, 

 which were made in 1844 by Bravais, in conjunction with 

 Martins and Lepileur, and compared at 35 stations, includ- 

 ing the summits of Mont Blanc (15,783 feet), of the Great St. 

 Bernard (8364 feet), and of the Faulhorn (8712 feet), the 

 above-named physicists made a series of inclination experi- 

 ments on the grand plateau of Mont Blanc (12,893 feet), and 

 at Chamouni (3421 feet). Although the comparison of these 

 results showed that the elevation of the soil exerted an in- 

 fluence in diminishing the magnetic inclination, observations 

 made at the Faulhorn and at Brienz (1870 feet in eleva- 

 tion) showed the opposite result of the inclination increasing 

 with the height. The different investigations on horizontal 

 intensity and inclination failed to yield any satisfactory 

 solution of the problem. (Bravais, Sur VIntensite du Mag- 

 net isme Terrestre en France, en Suisse, et en Savoie, in the 

 Annales de Chimie et de Physique, 3eme serie, t. xviii, 1846, 

 p. 225.) In a manuscript report by Borda of his expedition 



44 I would again repeat that all the European observations of incli- 

 nation \vhichhave been given in this page have been reckoned according 

 to the diyiion of the circle into 360 parts, and it is only in those obser- 

 vations of inclination which I made myself before the month of June, 

 1804, in the New Continent, that the centesimal division of the arc has 

 been, adhered to (Voy. aux Regions Equinox., t. iii, pp. 615 623). 



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