eee! Sh Se 
B. V. Marsh on the Luminosity of Meteors. 95 
The above table shows results thus obtained, together with 
some other facts bearing upon the subject. 
e most important as well as the most striking fact shown 
by this table, is that the quantity of latent heat in a given bulk 
of air is sensibly constant for all heights exceeding 30 miles. 
Below that point it decreases rapidly as we descend, being at 34 
miles only one-half of what it is at 80 miles. 
or convenience of illustration, let us assume as our unit of 
measure a cylinder 1 mile long and 1 foot in diameter—this 
being the space traversed by a globular meteor 1 foot in diame- 
ter in going 1 mile. Such acylinder will contain, at the s 
of the earth, 335 pounds (2342847 grains) of air. 
At the height of 3-48 miles it will contain 167 pounds, which, 
when condensed to the density of air at the surface, will evolve 
enough heat to raise the temperature of the original weight— 
say 3835 pounds—72°. 
At 34°30 miles it will contain 4 pound of air, which, condensed 
_ as before, will evolve heat sufficient to raise 335 pounds 144°, 
At 68°60 mi 1 i 
miles—the weight of air is only 2 grains but its 
condensation will raise 385 pounds 144°—and generally, the same 
bulk of air is capable of effecting the same result at any greater height, 
even to the extreme limits of the atmosphere. 
before it a bulk of air equal to our assumed unit of measure, 
which, compressed to the density of air at the surface of the 
earth, will give out heat enough to raise 835 pounds of air 144°. 
In one second it passes through ten units, and the heat evolved — 
will raise 8335 pounds 1440°, or the weight of the stone—two 
hundred pounds—2412°, being more than sufficient to bring the 
whole mass to an incandescent state. re 
But this heat is developed, not in the stone weighing 200 Ibs., 
but in a body of air, the total weight of which is at most only 
afew grains. The intensity of the heat in this small mass must 
therefore be proportionally greater. The table shows that at 
the height of only. 55 miles the heat is sufficient to raise the 
temperature of the whole mass of air encountered, more than 
nine million degrees; and at greater heights the intensity will 
ne in a geometric ratio, so that at 137 miles only it be- 
comes one hundred and fifty-eight millions of millions. 
It thus appears that we have the means of accounting for a 
brillianey of any imaginable intensity—the greatest splendor being, 
not in the meteor, but in the air which surrounds tt. 
icles of air which are in immediate contact with the 
stone (and those only) will of course part with a considerable 
