82 TRANS. ST. LOUIS ACAD. SCIENCE. 



The calculation for intensity, involving a redetermination of the 

 constant ^., and a determination of the change of the moment of 

 inertia of the magnet for a change of i° F. in its temperature, 

 were all made by mself. 



The gentlemen who accompanied me paid their own expenses, 

 or were aided by friends, and the other expenses of the work 

 were paid in part by Mr. Wayman Crow and Dr. W. G. Eliot. 



My thanks are also due to the following Railroads, which have 

 very kindly encouraged us with passes : St. Louis, Kansas City 

 and Northern ; Missouri Pacific ; San Louis and St. Francisco ; 

 Missouri, Kansas and Texas ; St. Louis, Keokuk and Northwest- 

 ern ; Missouri, Iowa and Nebraska. 



My thanks are also due to the gentlemen who accompanied the 

 expedition, who were often put to great physical discomfort ; and 

 to Mr. A. D. Jaynes of Sedalia, whose hearty cooperation and 

 personal aid were of great value. 



DECLINATION. 



The transit used in determining the meridian, and in observing 

 the magnet scale, was made by Jones of London, and had evi- 

 dently seen service. The vertical and horizontal circles were 

 provided with tangent screws and double verniers, reading to 

 the half minute. 



The magnet used in determining the declination was Cg, and 

 its axis was redetermined each day whenever this was possible. 

 In a few instances this was not done, but subsequent determina- 

 tions showed that no appreciable change had taken place. The 

 two collimator magnets were always carried in separate cases 

 suspended from the shoulder and with the south pole up, and 

 were protected with great care. 



The copper damper which accompanied the declinometer 

 was never used. The following device was found much more 



satisfactory. A thin brass, > 



wire, suspended in the angle 

 of the stirrup below the mag- 

 net, carried a light paddle of 

 thin sheet brass, which dipped l 

 into a vessel of glycerine. — ^.i 

 The lower edge of the paddle 1 



was slit vertically (as seen at a), and was bent upward into 



