1917—18.] Note on the Strathmore Meteorite of 1917 Dec. 3. 73 
in Perthshire. The area of the British Isles is one sixteen-hundredth of the 
surface of the globe ; so if we suppose that each fall amounted to, say, a 
hundredweight, and there were ten times as many falls upon our soil as are 
recorded, with a proportionate distribution over the rest of the globe, we 
find that the earth would acquire no more than 100 tons of meteoric matter 
in this form in the course of a year. We have only to compare this figure 
with the whole mass of the earth, 6 x 10 21 tons, to see how trifling it is. 
Even if we suppose the whole plane of the orbit of the earth, between us 
and the sun, to be equally endowed, the amount in existence would only be 
about a million tons. There is no reason that we should suppose it so 
endowed, but if we found ourselves led to do so. no cosmical consequences 
of any importance would follow. 
But there is nothing whatever in these bodies that would lead us to 
ascribe to them a remote, foreign and unfamiliar nature, or to ascribe their 
origin to an unknown region of space. They consist exclusively of very 
familiar constituents of the earth’s crust. They resemble certain volcanic 
stones, crystallised in a hurry. Is it possible that they are simply ejecta- 
menta from our own volcanoes? It seems fairly improbable. We have 
seen above that it is not easy to fire a projectile with high velocity right 
through the earth’s atmosphere, because it has to tear out the whole 
atmosphere in front of it, and in the course of doing so would generate a 
sudden and enormous heat that could hardly fail to ignite and shatter it. 
We may, if we like, postulate that in former times the earth had vastly 
more powerful volcanoes and a much thinner atmosphere than now, but 
that is trimming our facts to suit our theory, and reduces it all to an 
idle guess. But a cognate explanation is open that presents no difficulties 
that I can perceive. On the moon we know the volcanoes to have been 
immensely greater than on the earth, atmosphere almost non-existent, 
and gravity at the surface reduced to one-fifth of our own. I suppose 
that when great craters like Tycho and Copernicus were active, few 
undemonstrable things are less open to doubt than that they ejected from 
time to time fused masses which never fell back again upon the moon’s 
surface, which is only the thirteenth part of the surface of the earth. A 
relative velocity of between 1 and 2 miles a second would take them for 
ever out of the moon’s exclusive control. What, then, would become of 
them ? The moon is, strictly speaking, one of the sun’s planets, more 
literally than it is a satellite of the earth, and possesses the earth’s mean 
orbital motion round the sun of 18 mile/sec. The added velocity would 
be a small addition to this, and therefore any body ejected as I have 
supposed, would simply become another member of the earth and moon 
