OBSERVATIONS OF THE MAGNETIC FORCE. 
315 
Values of the Magnetic Force at Mr. Renwick’s Stations. 
Mr. Renwick’s observations consisted partly of determinations of the absolute 
horizontal force with a portable unifilar magnetometer, and partly of determinations 
of its ratios, by means of the times of vibrations of the magnet of the unifilar, of which 
the magnetism is assumed to have been constant. The absolute values of the total 
force are derived from the horizontal component obtained by both classes of obser- 
vations, by applying the Inclinations observed at the same stations, which will be 
found in the General Table of Inclinations in the sequel, where also the geographical 
positions of Mr. Renwick’s stations are given. The particulars of the magnetic 
determinations will be contained in the official publication of the United States Go- 
vernment: the results now communicated have been computed by Mr. Renwick. 
Table XL VII. 
Results of the Observations on the Magnetic Force made by Mr. Renwick in 1844. 
Station. 
Absolute hori- 
zontal force. 
Absolute 
total force. 
Stonington 
3-7479 
13-133 
Bridgeport 
3-7380 
13-050 
Greenport 
3-8501 
13-142 
Saybrook 
3-5636 
13-388 
New York (Columbia College). . . . 
4-1317 
13-883 
New York (Old Lunatic Asylum).. 
4-0913 
13-849 
Sandy Hook 
4-1270 
13-824 
Yale College 
3-8758 
13-514 
Stamford 
3-9429 
13-512 
Oyster Bay 
3-9526 
13-506 
Remarks. 
Vibrations and deflections. 
> Vibrations only. 
The determinations of the magnetic force which have been discussed in the pre- 
ceding pages, are collected in one view in the following General Table, No. XLVI1L ; 
which exhibits the names of the stations, their geographical positions, the observers, 
and the intensities of the Force; the latter are placed in separate columns according 
to the nature of the determination in each case, the relative values of the total Force 
being placed in the one column, and the absolute values of the horizontal component 
in another ; the former are expressed in the arbitrary scale, and are dependent on 
f‘836 as the force at Toronto; the latter are expressed in British units. A final 
column is added for the purpose of showing the total Force in absolute measure cor- 
responding to the determinations in the two preceding columns : when the deduction 
is from the horizontal component, the values in the final column are the horizontal 
force multiplied by the secant of the observed Inclination ; when from the ratios of 
the total Force, they have been computed by multiplying the respective ratios by 
13*896 
q; 836 . The number of separate results in the Table is 289, of which 222 are relative, 
and 67 are absolute determinations. The number of stations at which the force 
has been obtained by these observations is 234. Seventeen of the results at fifteen 
