B. V. Marsh on the Luminosity of Meteors. 97 
_ protection of the earth from collision with bodies approaching 
_ it with planetary velocity from without. The intruder is instantly 
surrounded with a fiery envelope heated to the greatest conceiv- 
able intensity, its surface is burned off or dissipated into vapor, 
e sudden expansion of the stratum immediately beneath the 
burning surface tears the body into fragments, each of Here 
retaining its —_— fa is saber & surrounded 
similar envelope, which produces like effects; and so on, nntil 
in most cases the whole is pve up or vanioriaa Bee ; 
Of the vast number of meteors seen, and which may fairly 
be presumed to embrace great variety of material, but very few 
are known to reach the earth, and these few are invariably found 
to be composed of the most incombustible substances—flinty 
stones or masses of iron. Such bodies ra penetrate the whole 
depth of the atmosphere with only a partial loss of substance, 
whilst those of a more combustible watts may be totally de- 
stroyed during the flight of a few miles. 
vaporize, while the sudden and violent expansion of the parts enngie's, ponent 
_ the fused es must or a iy cause ond itat ape: anche gets n of fragments. In 
short, there is no part of the phenomeno ich t his explanation does ae ‘ie 
Mere frietion against as atmosphere as dee by Poisson, seems quite insuffi- 
en uce incandesce 
Although no numerical maui are nase given, it might be supposed that this 
article tee those given above, but such does not appear to be the fa 
ion to which the mat pattie investigation ns of Poisson led him are 
thus eenciend (Ann. de Chim., 1825, xxiii, 841). “ Whence we conclude in general, 
rd 
c=(o-2ees)(E) & 
_ and the value of c’ can be deduced from that of ¢ by string it by &. As this 
> eee! k is tne than unity, we see that the specific heat of a gramme of air, 
and generally of any gas wha’ , will increase when the clatie fore, p, becomes 
In the above, ¢ represents the specific heat under constant pressure. 
ce’ “ “ sc volume. 
is the pressure. 
" ‘ with barometer at 29°92 in. 
— and be 5 and assumed =1-3750. 
cay specific heat,” and makes no mention of “latent heat” in 
looking this a and i ge writ to 
even o t misquot and assum: er seems 
Me ee i ve girs 4 ~~ heat” might be 
trea of ith the increase of is 
_ altogether too trifling to sr a the ae of an tion of the ie pheoherena te 
uest ao E 
at that hei nt leg ape stated is 589680 degrees. 
f tical dedue which has been 
ay ake agra pepsi erroneous by the sepermects of Berane’ who has shown 
the spec the same for all ; so that the explanation as it 
ce tied be entirely without gaadee 
an pub et -tapons Szrres, Vor. XXXVI, No. 106.—Juy, 1863. 
