382 Mr Barlow’s Electro-Magnetic Experiments. 
muth or inclination, the same motion takes place, which certain- 
ly appears to me to be wholly at variance with the doctrine that 
M. Ampere has endeavoured to establish. And if, instead of 
using the magnet, we leave the wire to the action of the terres- 
trial magnetism only, a similar effect, but in a less degree, is pro- 
duced every time the connection with the battery is established : 
and it is the same whether the wire be placed at N and S, E and 
W, or at any azimuth whatever ; a fact which seems to be equal- 
ly at variance with M. Ampere’s theory of terrestrial magnet- 
ism. 
“ Whether this ingenious author, for whose talents I enter- 
tain the highest respect, will be able to reconcile these pheno- 
mena with his theory, I am unable to say. If he can, no one 
will be more ready than myself to admit his doctrine ; being ful- 
ly aware of the great advantages which philosophy derives from 
the reduction of a variety of classes of phenomena to one gene- 
ral principle : at the same time we must be careful not to gene- 
ralize too quickly ; nor, in our anxiety to avoid the introduction 
of a force, hitherto unknown in nature, allow ourselves to leave 
imperfectly explained some of the most interesting facts yet eli- 
cited by experimental philosophy.” 
Art. XVII. — Description of the Lamps with Concentric Wicks $ 
and with a superabundant supply of Oil , as adopted in the 
French Light-houses *. 
rp 
JL. HE advantages of several concentric wicks in lamps, has been 
long ago pointed out by Count Rumford; and M. Carcel, in his 
ingenious mechanical lamp, had employed the happy idea of 
keeping the wick constantly Wet with a quantity of oil greater 
than it could consume. In applying tire contrivance of Carcel to 
the double, triple, or quadruple wicks of Count Rumford, MM. 
Arago and Fresnel, instead of raising the oil by a piece of clock- 
work as Carcel did, employed a reservoir higher than the wick, 
* This notice is abstracted from M. Fresnel’s Memoire sur un Nouveau Sys« 
feme d'Eclairagc des P hares, Paris 1802, already quoted in this volume, p, 165. 
