PLACES IN THE STATE OF OHIO, ETC. 



269 



minution of the magnetism in the two former by means of the appli- 

 cation of " keepers," strips of soft iron to join their dissimilar ends. 

 The vibrations with No. 3 were twice repeated, and extended each 

 time to five hundred, in number; and as the magnetism of the needles 

 is liable to decrease, but not liable to increase, I attach the greater im- 

 portance to the last result, and would therefore conclude that the hori- 

 zontal intensity at Greenwich is, to that at Cincinnati, as 1 is to 1-2037. 

 But little weight can, however, be attached to these observations, until 

 they shall have been verified by repetition, I am, therefore, very de- 

 sirous, that after I shall have fully ascertained here the properties of 

 these needles, I may be enabled to send them again to Greenwich, 

 have them vibrated satisfactorily there, and returned to be verified 

 again in America. 



It is not my intention, at this time, to go into the details of my ob- 

 servations on Intensity; this I will defer until my experiments shall 

 have been more extensive. I will now proceed to give you the results 

 of my experiments with the Dipping apparatus, at London and at se- 

 veral places in Ohio. 



August 20th, 1837, I proceeded to the celebrated station of West- 

 bourn Green, near London, where Captain Ross has made many of 

 his observations, and obtained the following results : 



No. of Needle. 



Polarity. 



Limb of In- 

 strument. 



Face of 



Needle. 



Indication. 



Mean. 





r 





r 



E 



E 



69° 15' 









A < 





E 



W 



69 431 











W 



E 



69 06 













W 



W 



69 40 





1. < 























1 



W 



W 



69 03i 









B < 



W 



E 



69 44 











E 



W 



09 10 







^ 





» 



E 

 E 



E 

 E 



69 24 



70 121 



69° 23'-25 









A < 





E 



W 



68 48 



i 









W 



E 



69 56 













W 



W 



68 40 





2. 







/- 



W 



W 



69 46 









B < 





W 



E 



68 49 











E 



W 



70 08i 







- 





^ 



E 



E 



68 47i 



69° 23'-4375 







69° 23'-3437 



