52 M A (i N E TIC S U K V E V 1 1 K P E N N S YL V A X I A 



have, from Dr. Locke's observations at Baltimore in 1841, at St. Mary's. 4.261; at 

 the city, 1.238; mean. 4.250; which gives for Philadelphia 4.146. At Philadelphia 

 we have Prof. Loomis' determination in 1839, 4.149 (Chestnut Street), and Dr. 

 Locke's, 4.172, at the Girard College, the mean of which will be 4.160. This value 

 may he adopted for the 1840 scries. 



For the stations occupied in 1841, the mean of the absolute values used in 1840 

 and 1843 for Philadelphia, viz., 4.166, has been used as the base number. 



Accordingly, we obtain the following magnetic horizontal intensities, expressed 

 in terms of the absolute scale (British units): — 



Barrisburg .... 

 Huntingdon .... 

 Boinewood .... 

 Johnson's Tavern 



Irwin's Mill .... 

 Baltimore .... 



Philadelphia (base) 



Williarasport .... 

 Curwinsville .... 

 Mercer .... 



Erie . 



Ellicottville .... 

 Bath ..... 

 Silver Lake .... 

 Milford .... 



Philadelphia (base) 



Philadelphia .... 

 Union Collegi Schenectady 

 Syracuse .... 



( leneva ..... 

 Niagara Fall.- .... 

 Toronto (base i ... 



Ogdensburgh .... 

 Montreal .... 



Connection of tlu European and American Series of 1*:!(>, 'ML '38, "//'/ 1840.' 



The series of observations made in Europe in the years 1836, '37, and ":is. when 

 the same cylinder and liar magnets were used, previously and subsequently used at 

 Philadelphia and other places, give us additional means of introducing the absolute 

 measures of the horizontal force, though in a somewhat circuitous way. 



According to General Sabine, the total force at Woolwich, in June, 1846, may 

 he taken at Kt.oSS; Dr. Lamont thinks that the total force in Europe has hut a 

 small, if any change; we may therefore take 10.388 to represent the total force in 



1 Art. IX, Transactions American Philosophical Society, Philadelphia, Vol. VII, new series, Part 1, 1S4U. 

 Observations el' the Magnetii tnten e. .it twenty one stations in Europe. By A. D. Bache, I.I..I'., President ot 

 the Girard College of Orphans. 



