ON THE MAGNETIC INTENSITY OF THE EARTH. 5 
Station. Late. Lat.* Long.* Dip. Time of 
Vibration. 
rath SER 20 Sept., 1791) 4824 | 35534 | 7130N| 2-02 
Teneriffe .........+2. 21 Oct, 1791 | 28 28 343 42 | 6225N.| 2:081 
Van Diemen’s Land |11 May, 1792] 433828S.| 14657 | 7050S.| 1-869 
Amboyna ......... --.| 9 Oct., 1792 | 3428.| 12808 | 20878.| 2-403 
Van Diemen’s Land | 7 Feb., 1793 | 48348.) 14657 | 7222S.| 1-850 
Surabaya ....eceeeee 9 May, 1794) 7148.) 11242 | 2520S.| 2-429 
The times of vibration are in infinitely small ares, being reduced by M. 
de Rossel, by means of a table which accompanies the observations in the 
original publication. 
M. de Rossel’s observations at Van Diemen’s Land were 
made at a port on the S.E. part of the island. Capt. Fitz Roy 
has recently determined the value of the intensity at Hobart 
Town, about 40 miles north of M. de Rossel’s station, to be 
1-817, in terms of a comparative scale in general use adopted 
in this Report, of which an explanation will be given in the 
sequel. Suffice it at present to say, that in the same scale the 
force at Paris = 1348, and at London 1°372. Capt. Fitz Roy’s 
observations will be found in their place in the course of this 
Report. If we take his value of the intensity at Hobart Town 
for the force at M. de Rossel’s station, we have 1:097 as the 
force at Amboyna. By means of Capt. Fitz Roy’s observation 
at Van Diemen’s Land, I have been thus enabled to connect 
M. de Rossel’s determination at Amboyna with Europe, and it 
is accordingly entered in the general table. 
Humboldt, 1798-1803.—These observations were made in 
the course of M. de Humboldt’s well-known journey to equi- 
noctial America. Various partial notices of them have appeared 
at different times and in different works, but a complete account, 
communicated by M. de Humboldt himself, may be found in 
the xvth volume of the Annalen der Physik, from which the 
results employed in this memoir are derived. The observations 
were made with a dipping needle of Le Noir, selected by 
M. Borda. It vibrated considerably longer before coming to 
rest than the needle employed by M. de Rossel, so as to allow 
the number of vibrations performed in ten minutes to be taken 
as the measure of the intensity at the different stations. The 
time of vibration at Paris was observed in October 1798. be- 
* All the longitudes in this Report are east of Greenwich, unless otherwise 
‘expressed ; and all the latitudes are north unless they are designated otherwise. 
