AT TWENTY-ONE STATIONS IN EUROPE. 



85 



as great a one is to be found among- the foregoing results. The determinations 

 of the dip at Paris agree very well with that given by Professor Forbes, on 

 the authority of M. Arago, in July, 1835,* namely, 67° 24'.0. An annual 

 diminution of dip of 2'. 8 would give, in August, 1837, 67° 18'.2, while I found 

 67° 21 '.4; and in July, 1838, 67° 15'.6, while my result was 67° 16'.5. 



It is obvious, then, that my value of the total intensity is correct or not, ac- 

 cording as the horizontal intensity has or has not been accurately determined. 

 I shall return to this, after stating the results obtained by the statical method 

 of Professor Lloyd. As the observations in 1837, by this method, were made 

 at the short interval of a month from each other, I have not thought it neces- 

 sary to apply a correction to them, the whole loss of magnetism, during the 

 year, by either needle, having amounted to less than 0.01. 



Observations f 07' Total Intensity at London and Paris, by the Statical Method. 



Place. 



Date. 



Needle. 



Temp. 



Dip when 

 loaded, 



or 

 Angle e. 



Dip reduced 



to August, 



or 



Angle cT. 



Total 



Intensity, 



or 



Cor. 9 



Month. 



Year. 



Fah. ° 



Sui(/ — 9) 



London 



Paris 



London 



Paris 



London 



Paris 



London 



Paris 



June 

 Aug. 

 June 

 Aug. 

 Aug. 

 July 

 Aug. 

 July 



1837. 



(( 



U 



1838. 



<( 



No. 1, 

 No. 2, 

 No. 1, 

 No. 2, 



741 



72^ 



74i 



721 



65 



75 



65 



77 



21° 



24 



19 



22 



22 



25 



19 



23 



59'.0 

 47.3 

 13 .5 

 48 .2 

 31 .3 

 41 .7 

 59.4 

 12.5 



69° 

 67 



69 

 67 



17'. 5 

 21 .0 



12.3 

 16.2 



0.979 

 0.976 

 0.979t 

 0.980t 



The horizontal intensity deduced from these results by using the dip already 

 given, is 1.065, agreeing closely with the determination by the method of 

 vibrations. This latter determination rests upon 4072 oscillations at one 

 station, and 6426 at the other, besides the verification by the statical method.. 

 The foregoing results are collected in the following table. 



* See the paper of Professor Forbes before referred to, in the Edinburgh Transactions, vol. xiv. 

 p. 27. 



t A small correction has been applied for the eflfect of temperature, amounting to 0.003 and 

 0.002 in the two cases respectively. 

 VII. — W 



