Prof. Forbes on Terrestrial Magnetic Intensity, 363 



count for the fact, that, if we pass from Southern Europe to 

 Northern, the westerly winds generally prevail at the expense 

 of the south-westerly. 



For the positions stated in C, proofs will be found in some 

 of my previous memoirs. They might be considerably aug- 

 mented in number, which however does not seem to me ne- 

 cessary. 



XLV. Account of some Experiments made in different Parts oj 

 Europe, on Terrestrial Magnetic Intensity ', particularly with 

 reference to the Effect of Height. By James D. Forbes, 

 Esq., F.Il.SS. L. $ E., $c, Prof. Nat. Phil, Edinb. 



[Continued from p. 260, and concluded.] 



30. TJUT to return to the calculation of the first group of 

 -*-* observations, those including the alpine country of 

 Switzerland, Savoy, and Italy. If we arrange the observations 

 relatively to Geneva as a fundamental station, taking the data 

 from Table VII. and writing the equations of condition in the 

 form (3.) art. 28, where a x denotes the excess of northern 

 latitude of the given station above that of Geneva in minutes; 

 b x the excess of eastern longitude in minutes of a degree ; c x 

 the excess in height, reckoned in hundreds of English feet in 

 round numbers (using of course negative signs to represent 

 the reverse of all this), we shall have the following equations 

 of condition, distinguishing from one another the absolute 

 numbers obtained by the two needles, in order that they may 

 be separately calculated. 



Table VIII. 

 Equations of Condition for the Alpine Series. 



By No. I. By <« Flat." 



Geneva (Aug. 1832) 0'*+ <fy+0'z+3r = -002 -005 



Geneva (Nov. 1832) 0*+ 0#+ Oz+dl' = — '002 — 005 



MontSaleve — 6*+ 2 < y+32z+M' = -001 -002 



MontBreven — 16*+ 41 y+7\ z+l V = -013 -024 



5. Chamouni — 17*+ 43y +21 z + S I' = -009 -005 



Jardin -17*+ 50^+77 z+SI' = -007 009 



Col des Fours —27*+ 36#+76z+S I' = -012 



Aoste —28*+ 71y+ 6z+SI' = -020 '018 



St. Bernard —20*+ 61^+68«+8I'= "006 000 



lO.Martigny — 6*+ 56#+ 3z+BI' = -007 '004 



Interlaken 30*+103#+ 6z+ll' = — 008 —'009 



Schmadribach .... 19*+104j/+39z+dl' = -003 —'002 



Grir.delwald (1.) .. 26*+ 1 13^+24 z+lV = —001 000 



Grindelwald (2.) .. 26*+113y+21 z+lV = — 004 '007 



15. Meyringen 32*+ 123^+ 7 z+ IV =—001 



Grimsel 22*+ 130^+49 z+d 1' = —002 —007 



Munster 18 *+ 128^+29 z+ 3 I' *= -002 — 003 



3 A2 



