THE LOST COMET AND ITS METEOE-TRAIN. 
149 
Ilow small must be the prospect of seeing a flight of bodies so 
exceedingly minute compared with the average space occupied 
by each. It is, indeed, easy to estimate the luminosity of such 
a flight regarded as a whole, if of given depth and at a given 
distance from the sun. Thus, suppose the flight of a million 
miles in depth, and at the earth’s distance from the sun. Along 
a range of a million miles there would be less than 10,000 
meteors. N"ow, granting each to have a disk one square inch 
in real area, we should have a total area of 10,000 square 
inches (that is, feet square). And the ratio of this area to 
108 miles square gives the ratio of the luminosity of the 
meteor-cloud (when of the given depth) to the luminosity of a 
surface illuminated by the sun at the earth’s distance — (say, the 
moon, for example). How 108 miles square, or 11,664 square 
miles, contain 11,664 x (1,760)'** x (36)^ square inches, or 
roughly (for great nicety would be useless in such a problem) 
10,000 X (2,000)^ X (35)^ square inches ; so that the ratio we 
require is 1 to (70,000)^ or 1 to 4,900,000,000. That is, the 
luminosity of the meteor-cloud would be one-4,900,000,000th 
only of the moon’s, and necessarily the meteor-cloud would be 
quite undiscernible. Hence we may be assured that if the object 
seen by Pogson was connected at all with the meteor-cloud 
through which the earth passed on November 27, he saw a very 
much denser part of the meteor-cloud; and there is no reason why 
this dense portion or nucleus of the meteor-cloud may not have 
been at a considerable distance from the earth on the 27th of 
last November. This consideration would serve to remove 
some of the more perplexing circumstances of the recent 
observations. 
