BETWEEN THE UNITED STATES AND MEXICO. 



251 



ions f( 



The 



deflections were measured on a nine-inch circle, according to Lament's method, in which the 

 two magnets remain at right angles. In the vihration experiments, the time of 400 vibrations 

 is usually observed, of which six values are obtained in each set, in the usual way. Experi- 

 ments to determine the moment of inertia of the magnet and its attachments were made repeat- 

 edly by vibrating it loaded with a brass ring, marked No. 11, of which the outside diameter is 

 2.899 inches, the inside diameter 2.462 inches, and the weight 719.90 grains ; hence its moment 

 of inertia, K, = 9.04, expressed in feet and grains. The magnet used, marked X 7, is of the 

 usual form, being a hollow cylinder of 0.3 inch in diameter, and 3.G6 inches in length, and 



carrying a mirror 



Wasl 



1856, by vibrations at temperature near 30° and 70°, and was ascertained 



2 



0.0003. 



The following is an abstract of the observations ; to which is to be added, that, in the experi- 



without the inertia rins, the effect of 90° of torsion was 7'. 5; in those with the ring, 15'. 



ments 



of observations fc 



A 



VIBRATIONS. 



F 



n 





DEFLECTIONS. 





Station. 



Without ring. 



1 Wiih ] 



ring. 





r = 1.3 feet. 



... .. -_ 



Date. 





T 



Time of 1 vibr. 



Temperature. 



1 



T 



r 



Timeofl vibr. 



Temperature. 



u 



Temperaturt. 



1 





3.795 

 3.795 



O 



1 



74.5 

 59 



1 



7.946 

 7.935 



1 







69.5 

 63 



3 29.6 

 28.7 

 30.0 



1 



1 

 • 



61 



53.5 



41 



i 



1855. 



i 



F 

 F 





3.795 



3.817 

 3.823 

 3.826 



70 



71.5 



83 



75 



63 



1 



63 

 61 

 73 



1 

 1 



1 



1 



7.941 



t 

 t 





69 



2 29.4 



2 31.2 

 2 31 



2 29.9 



52 



59 



67.5 ! 

 64.5 



Jauuary 4. 







4 



i 



1 

 P 



4 



7,983 i 



1 





76 





J 



1 



1 



— --^ ' . f ' — *^ 







3.822 



3.770 



3.791 



3.751 

 3.757 



L 



7.983 ' 



b 



i 



7.910 i 



\ 



f 



1 



76 

 70 



2 30.7 



64 ' 



1 



March 1. 



-^f^ ^ 



1 March 22. 





1 

 1 

 1 





April 3. 



^^ T ■— 0m«.n->-k^r« 







S 30.0 i 

 2 W.O 

 2 27.0 



64.5 

 66.5 

 65 



t 





V 

















3.754 



3.776 



3.778 

 3.764 



67 



78.5 

 82.5 

 81. 



1 





5 29.0 



1 



65 



1 



1 



J 

 1 



ri 







p 



April 19. 





i 



■ n 



■1 



i 

 1 



J 



1 



1 



r 



L 



L 



1 







1 







T 77T 



SI 







1 



April 28. 





^9 9 to ^• 



t 



3.798 79 



f 



\ 



f 



1 

 i 



1 



1 



i 



! 



' « • ■ • 



1 



1 

 1 



1 



1 

 1 



h 







1 



3.894 



74 



1 







^ ftfti ^ 7n 



+ 



1 





3 





1 M4yl4. 





3.805 



94 



i ' 



7,949 



i 

 1 



« ■ » • 



80 



2 26.5 

 25.2 



81.5 

 63 







1 



1 







1 



■_ _ 







2 25.85 



62 



June 16. 



