SOUTHERN CALIFORNIA ACADEMY OF SCIENCES — gr 
than, 26 miles per second, and that of morning shooting stars 
is greater. 
Moreover, as the earth speeds on in its orbit its front is the 
sun-rise side and its rear is ever in the evening shade. We 
therefore see more shooting stars in the early morning than in 
the evening—just as in a walk or drive more people meet us 
than overtake us. 
Mass or Weight 
To find a shooting star’s weight requires the help of an as- 
sistant observer at one of the stations. When preparing for 
the observations at W and L, Fig. 1, suppose an incandescent 
lamp of 16 candle-power was placed at an elevation above a 
high hill west of W, plainly visible to the assistant at W and 
distant from him just one half mile. 
The assistant does one thing only. He compares the bright- 
ness of the lamp high up in the west with the brightness of each 
shooting star noted, and in each instance records his judgment 
as to the relative brightness of star and lamp. Of this he soon 
judges quickly and correctly, especially when the flitting star 
and the distant light are about equally bright. Even an un- 
practised eye decides readily which of two nearly equal lehts 
is the brighter. Of hundreds asked by the writer which of the 
twin stars, Castor and Pollux, is the brighter, not one decided 
incorrectly. 
Say that to the notes of Fig. 1 the assistant at W added: 
“brightness of shooting star and ineandescent lamp just 
equal;’’ also, that the calculations of Fig. 2 proved that the 
shooting star’s average distance from W was 60 miles. This 
data-distanee of lamp, distance of star, their equal brightness 
—and established principles of Physies, will give the shooting 
star’s mass or weight. 
Since to make a one candle-power light requires 150 foot- 
pounds of work or energy per minute, the 16 candle-power 
light on the hill was produced by 16 times 150 ft.-lbs. of energy 
per minute, or by 1-10 of 16 times 150 ft.-lbs. of energy every 6 
seconds; that is, it was made by using every 6 seconds 240 
ft.-lbs. of energy. 
The shooting star 60 miles off and shining 6 seconds, as ob- 
served, was just the brightness of the 16 candle-power light 1% 
mile away. 
The intensities of two such lights—hehts equally bright at 
different distances—are as the squares of the distances. In 
this instance then, their intensities were as 602 to (14)?, or as 
14400 to 1. That is, the energy which produced the shooting 
