78 



To the first observation, a correction is applied, from observation at a 

 station where the dip is accurately- known, to obtain the true dip. 

 The second being repeated at different places, the elements necessary 

 to determine the relative intensities are known ; and the approximate 

 formula, connecting these observed elements with the relative intensi- 

 ties of the magnetism of the places where the change of intensity is 

 not great, is very simple. 



Prof. Bache showed an instrument, made by Robinson, of London, 

 of the usual construction, for determining the magnetic dip, with 

 needles for the employment of Professor Lloyd's method. He also 

 referred to a method proposed by Professor Christie, of Woolwich, 

 similar in principle, but differing in detail, and showed the needles 

 for applying this method. 



Prof. Bache further stated, that he had caused the method of heat- 

 ing these needles to the temperature of boiling water, to bring them 

 to a permanent magnetic condition, as proposed by Prof. Christie, to 

 be tried by Mr. Robinson. It had not proved successful. 



Mr. S. C. Walker made a verbal communication on the 

 parallax of the star, 61 Cygni, recently investigated by Mr. 

 Bessel, and described the nature of the researches by which 

 this important point had been established. 



Stated Meeting, March 1. 

 Present, eighteen members. 

 Mr. Du Ponceau, President, in the Chair. 

 The following donations were received: — 



FOR THE LIBRARY. 



The Life of George Washington. By Jared Sparks. Boston, 1839. — 



From Mr. Sparks. 

 The Library of American Biography, conducted by Jared Sparks. 



Vols. VIII, IX, & X. Boston, 1837 & 1838— From the same. 

 The Transylvania Journal of Medicine. Vol. XI. No. 2. For 



April, May, and June. Lexington, Kentucky, 1838. — From the 



Editors. 



