72 
Proceedings of the Royal Society of Edinburgh. [Sess. 
density <j. Then after jp sec., it is easily seen that the common velocity 
would be reduced to 
n/{ 1 + 5280 pjia/cp} ; 
for example, suppose c is 1 foot, p = 3, <r = p q of density at the earth's 
surface, then whatever n is to start with, the velocity will be reduced to 
less than 1 mile/sec. after about 25 secs. The subsequent reduction of speed 
is more gradual and is easy to understand. 
As the speed is reduced from, say, n mile/sec. to 1 mile/sec., the mass in 
motion, including the air, increases from, say, m to nm, and, in consequence, 
kinetic energy is lost to the amount \mn l — \mn — \mn (n — 1). This will be 
represented by potential energy of compression and heat in the mass of air 
thrust in front of it by the meteorite. If we suppose that ^ = 10 mile/sec., 
the loss would be 1*2 x 10 9 ft.-lbs. of energy for each lb. of the body’s mass. 
Suppose the specific heat of the body is 0 '2 ; then the hundredth part of 
this lost energy communicated in return as heat from the compressed air in 
the midst of which the body is now moving would raise its temperature 
throughout by more than 2000°. 
Hence there is not the least difficulty in understanding how the surface 
becomes fused and incandescent and the stone flies in pieces. At first it 
sounds a paradox to say that the air subsequently cools the stone. But this, 
too, is easy to follow, for as the speed diminishes the compressed air, which 
is the depositary of the energy lost, readily escapes from the neighbourhood 
of the stone, and its surface is brought continually into contact with fresh 
portions of unheated air which rob it of the heat it has already acquired. 
The process is facilitated by the explosion, which increases largely the 
surface from which loss takes place. I shall not attempt, nor am I qualified, 
to describe the meteorite technically. This is the work of a mineralogist, 
and the previous examination of it will require a considerable time. It is, 
however, obviously an aerolite, that is to say, of stony character. It has the 
usual depressions, or “ thumb marks,” and streaks or stream-lines upon its 
thin, fused, blackish skin. If it follows the rule for such stones, we may 
expect it to be composed of nothing but very familiar terrestrial elements, 
with certain peculiarities of crystallisation, which, according to Mr L. Fletcher, 
our leading authority on these matters, are characteristic of a hasty process. 
The stone is said to resemble certain volcanic tuffs. I shall conclude with 
a few remarks upon the astronomical aspect of this visitor from space, and 
as we have so little fact, a slight range of speculation may be allowed. 
The quantity of these bodies which the earth picks up is not large, upon 
the most generous estimates. Some twelve known falls are registered 
within the British Isles in the past 100 years — two of which have occurred 
