© 
be computed approximately their mean lengths. For 
___ The two limits for the mean distance given above indicate 
202 H. A. Newton on Shooting Stars. 
distributed uniformly over the surface of the sphere, and if0 — 
be a point without the sphere whose distance from the center of 
the sphere is 6, then will the mean value of the angles at 0, — 
tw a 2 
O55: 
he mean effect of the foreshortening by perspective may — 
therefore be thus expressed. Let a diameter of the sphere be 
bent into the are of a circle whose radius is b; then the angleit — 
subtended by all these diameters, be equal t 
angles to the line of vision, for those would be down near thé — 
horizon, and would be copcealed by mists and smoke. It seems 
probable that in this ease the mean effect of foreshortening would 
12°-6x *, or about 1604. 
12. Mean length of the visible part of meteor-paths.— Ero pat 
mean distance and mean angular length of the meteors sa 
mean length, and b the mean distance, we have : 
as i =X16°-04 
=a I= 0'280. 
1¢ mean length is less than 65, and greater than 39, <V0 
