THE EARTH IN METEORIC SHADO W. 171 



whether the quantitative loss of heat during, say, 

 three days of the interposition of a meteor stream 

 could produce any measurable effect. 



Suppose a meteor stream to be a million miles 

 through, in the direction towards the sun (from the 

 -earth), and to be so broad, supposed to be seen edgewise 

 as to cover the whole breadth of the sun during three 

 days of the earth's motion in her orbit. Then the 

 region of meteor stream space actually intercepted 

 between the earth and the sun, would obviously be a 

 frustum of a cone, having the sun at its base, and 

 the earth near its apex. But we need not trouble our- 

 selves to consider this region as other than a cylinder, 

 a million miles high. Supposing it to be near the 

 sun (as we 'must consider any meteor system visible 

 during a total eclipse to be), we may set the diameter 

 of its base at about 800,000 miles ; whence it follows 

 that its volume would be about 500,000,000,000,000,000 

 cubic miles. If we assume that there is but one 

 meteor, one inch in diameter, in every 5 cubic miles, it 

 would follow that at each instant during the three days* 

 passage there are interposed between the earth and 

 the sun (members of that meteor system) no less than 

 100,000,000,000,000,000 meteors, each one inch in 

 diameter. Being so near to the sun, these meteors 

 would each hide a space equal to a circle-inch (that 

 is, a circle an inch in diameter) of his surface from 

 our earth's view. Now, in a circle mile there are 

 nearly 1,000,000,000 circle-inches. Hence it follows 

 that, apart from the very cases in which these widely 



