320 EIGHTH REPORT — 1838. 



servations referred to serve to determine the value of the mag- 

 netic force at the stations at which they are made relatively to 

 each other, but not relatively to other parts ofthegme.^nA 

 they were not. therefore, avadable for my report The Ame- 

 rican observations were made with magnetic needles inclosed 

 "a vacuu;; apparatus, which Mr. Bache had devised, with the 

 view of avoiding some of the anomalies occasionally experienced 

 by other observers. They were made with extreme care, and 

 were remarkable for minute attention to all those circumstances 

 which conduce to the accuracy of the results. 



END OF THE REPORTS. 



