112 COSMOS. 



the section on Magnetic Intensity, how very few localities 

 were able to afford any certainty as to this question, because 

 the distance between the points to be compared together 

 must be so small as to leave no ground for suspecting that 

 the difference found in the inclination may be a consequence 

 of the elevation of the soil, instead of the result of the curv- 

 ature of the isodynamic and isoclinal lines, or of some great 

 peculiarity in the composition of the rocks. I will limit 

 myself to the four results which I thought, at the time they 

 were obtained, showed more decisively than could be done 

 by observations of intensity the influence exerted by eleva- 

 tion in diminishing the dip of the needle. 



The Silla de Caracas, which rises almost vertically above 

 La Guayra, and 8638 feet above the level of the sea, south 

 of the coast, but in its immediate vicinity, and north of the 

 H town of Caracas, yielded the inclination of 41°-90; La 

 Guayra elevation 10 feet, inclination 42 o, 20; the town of 

 Caracas, height above the shores of the Rio Guayre, 2648 

 feet, inclination 42°-95. (Humboldt, Voy. aux Reg. Equi- 

 nox., t. i., p. 612.) 



Santa Fe de Bogota : elevation 8735 feet, inclination 

 27°*15 ; the chapel of Nuestra Sefiora de Guadalupe, built 

 upon the projecting edge of a rock, elevation 10,794 feet, 

 inclination 26 o, 80. 



Popayan: elevation 5825 feet, inclination 23°-25 ; mount- 

 ainous village of Purace on the declivity of the volcano, ele- 

 vation 8671 feet, inclination 21°-80; summit of the volcano 

 of Purace, elevation 14,548 feet, inclination 20°*30. 



Quito: elevation 9541, inclination 14 0, 85 ; San Antonio 

 de Lulumbamba, where the geographical equator intersects 

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

 feet, inclination 16 o, 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 

 neighboring kinds of rock, for me to enter fully into the 

 details of the following observations : the Hospice of St. 

 Gotthard, 7087 feet, inclination GG° 12'; compared with 

 Airolo, elevation 3727 feet, inclination G6° 54' ; and Altorf, 

 inclination 66° 55 y ; or to notice the apparently contradict- 

 ory data yielded by Lans le Bourg, inclination 6G° 9', the 

 Hospice of Mont Cenis, 6676 feet, inclination 66° 22', and 

 Turin 754 feet, inclination 66° 3'; or by Naples, Portici, 

 and the margin of the crater of Vesuvius; or by the summit 



