406 
HISTORY OF MAURITIUS. 
Inclination * of the Needle of the Compass. 
Although the inclination seems to be the first property of the magnet, the obser¬ 
vations on that subject have been neglected, either because their utility have not been 
perceived, or for want of proper instruments. 
“ M. l’Abbe de la Caille being possessed of better instruments than any of his 
predecessors, and employing all that precision which is known to have accompanied 
his operations, found no inclination at iij° south latitude. With the individual 
compass of M. l’Abbe de la Caille, eighteen years after him, I found no inclination 
in nearly the same situation, or at io^°. This fact, therefore, is incontestible. 
“ When M. l’Abbe de la Caille gave me his compass, he engaged me to repeat 
the observations which he had made ; because, in presenting it alternatively to the 
north and the south, he found, to the south of the Line, an inequality in the inclination 
as far as 3 0 ; and he did not believe that this difference arose, as M. Bernoulli thought, 
from any defect of equilibrium in the original construction of the instrument. 
“ On observing with the utmost care, and in repeated experiments, the inclina¬ 
tion in the Isle of France, we determined the difference to be from 2° to 3°. 
“ The fleur de lys to the north - - 53 0 37' 
--to the south - - 5214 
“ That great astronomer observed the inclination in his voyages, but they are 
confined to the Isle of France. It appears that he entertained no idea of the manner 
in which the compass is affected in the Ethiopic and Indian seas: nevertheless, he 
must have been surprised on finding the inclination of the compass at 52°; while he 
observed it to be about 20° in the same latitude as the Isle of France, on this side 
of Africa. 
M. de la Caille perhaps imagined, that this difference of 32 0 might proceed, in 
some measure, from the difference in the longitude of the two places where he had 
made his respective observations, as that amounted to about seventeen hundred 
leagues. 
“ In the year 1762, when I was in the Bay of D’Antongil, in the Island of Mada¬ 
gascar, in of south latitude, I observed the inclination to be 46°, and conse¬ 
quently, that the needle could not be horizontal at the latitude of ii^°, as M. de la 
Caille had seen it in nearly the same latitude, on the other side of Africa. 
“ In the year 1766 ,1 repeated this observation, on board one of the King’s ships, 
* For the variation, see the Chart of the Ethiopian Archipelago, p. 362. 
