40 



Magnetic Survey of the East of France in 1869. [Nov. 23, 



Myans (near Chambery), Villefranche, St. Etienne, Clermont, Moulins, 

 Paris, Douay, and Boulogne. 



The magnetic elements are reduced to the epoch January 1st, 1869, 

 the same as that adopted for the western stations. 



Station. 



Avignon 



Boulogne 



Clermont 



Dijon 



Pole 



Douay 



Grenoble 



Issenheim 



Lyons 



Marseilles 



Metz 



Monaco 



Montpellier .... 

 Mont Holland . 



Moulins , 



N. D. de Myans 



Paris 



Eheims 



St. Etienne 



Strasbourg 



Villefrancke .... 



Dip. 



61*841 

 67-126 

 63*607 



64- 409 

 64*213 

 66-785 



62- 903 

 64*601 



63- 268 

 60*576 



65- 458 

 61*368 

 61*614 

 64*260 

 64*081 



62- 875 

 65-859 

 65*936 



63- 063 



64- 687 

 63*498 



Declina- 

 tion. 



Inten- 

 sity. 



16*046 

 18*227 

 16-460 

 16*612 



16- 084 



17- 991 

 15-822 

 I 5'794 



15-691 



15- 976 

 14- 524 

 l6 *545 



16- 487 

 15*182 



17- 260 

 16-722 



14- 910 



15- 578 



16- 942 



9-7927 

 10*1511 

 9 9010 

 9-9418 

 9-9307 

 10-1301 

 9-7293 



9*95 8 5 

 9-8826 

 9-6092 



IO'OOI2 

 9*7189 



9*7512 

 9-9692 

 9-9190 

 9-8293 



10*0618 

 10*0967 

 9-8472 

 9*9405 

 9-8853 



Horizontal 

 Force. 



4*6224 



3'9458 

 4-4013 

 4-2943 

 4-3201 

 3*9931 

 4'43i7 

 4*2714 



4*4454 

 47207 

 4*1541 

 4-6571 

 4-6358 



4*3295 

 4-3356 



4-4815 

 4-1151 

 4*1170 

 4-4609 

 4-2502 

 4*4111 



The secular variations of these several elements are — 0°*054, — o, 1696, 

 + 0*0047, and — 0*0195. The yearly acceleration will therefore he 

 — 0° 00082 for the dip in 1863*5, the value found by General Sabine for 

 the epoch 1780 to 1830 being -0°*00085. 



As regards the horizontal force, the secular variation in the east of 

 France is considerably less than in the west ; hut the change for the whole 

 of France is almost identical with that deduced by Dr. Lamont for 1858, 

 the yearly acceleration being less than 0*000007. 



A comparison of the lines of equal dip, declination, intensity, and hori- 

 zontal force, deduced from the observations taken in the east and west of 

 France, leads to the following conclusions. 



The isoclinals are found to be rather further apart and more inclined to 

 the geographic meridian, but receding less quickly from it, in the east than 

 in the west ; the isogonics are more distant from each other, but make a 

 less angle with the meridian, in the east than in the west ; but the results 

 obtained from the declination observations of 1869 are less trustworthy 

 than those for 1868, on account of the unsteadiness of the new theodo- 

 lite. 



The distance between the isodynamics does not sensibly vary for east 



