28 
FALLING STABS. 
which we touch it remain luminous for two or three minutes, 
as is observed in breaking the shell of the pholades. If we 
rub wood with the body of a medusa, and the part rubbed 
ceases shining, the phosphorescence returns if wo pass a dry 
hand over the wood. When the light is extinguished a 
second time, it can no longer be reproduced, though the 
place rubbed be still humid and viscous. In what manner 
ought we to consider the effect of the friction, or that of the 
shock? This is a question of difficult solution. Is it a 
slight augmentation of temperature which favours the phos- 
phorescence ? or does the light return, because the surface 
is renewed, by putting the animal parts proper to disengage 
the phosphoric hydrogen in contact with the oxygen of the 
atmospheric air? 1 have proved by experiments published 
in 1797, that the shining of wood is extinguished in hydro- 
gen gas, and in pure azotic gas, and that its light reappears 
whenever we mix with it the smallest bubble of oxygen gas. 
These facts, to which several others may be added, tend to 
explain the causes of the phosphorescence of the sea, and of 
that peculiar influence which the shock of the waves exer- 
cises on the production of light. 
When wo were between the island of Madeira and the 
coast of Africa, we had slight breezes and dead calms, very 
favourable for the magnetic observations, winch occupied me 
during this passage. We were never weary of admiring 
the beauty of the nights ; nothing can ho compared to the 
transparency and serenity of an African sky. We were 
struck with the innumerable quantity of falling stars, wliich 
appeared at every instant. The farther progress we made 
towards the south, the more frequent was this phenomenon, 
especially near the Canaries. I have observed during my 
travels, that these igneous meteors are in general more 
common and luminous in some regions of the globe than in 
others ; but I have never beheld them so multiplied as in the 
vicinity of the volcanoes of the province of Quito, and in 
that part of the Pacific ocean which bathes the volcanic 
coasts of Guatimala. The influence which place, climate, and 
season appear to exercise on the falling stars, distinguishes 
this class of meteors from those to which we trace stones 
that chop from the sky (aerolites), and wTiich probably exist 
beyond the boundaries of our atmosphere. According to 
