382 
POPULAR SCIENCE REVIEW. 
I cannot bub regard myself as most fortunate in finding the 
first confirmation of my views (i.) coming from one of the 
most eminent astronomers and physicists of the day, (ii.) 
bearing upon one of the most definite and positive of my vati- 
cinations, and (iii.) relating to one of the most interesting 
subjects in the whole range of recent astronomical research. 
It will be in the remembrance of many readers of this 
magazine that, nearly four years ago, Dr. Huggins succeeded 
in showing that the bright star Sirius is travelling at an enor- 
mously rapid rate away from us. In other words, besides that 
rapid thwart motion which is shifting the place of this star 
upon the heavens, the star has a rapid motion of recession. In 
the paper called “Are there any Fixed Stars,” in the “Popular 
Science Keview ” for October 1868, the nature of the means 
by which this discovery was effected was fully described and 
explained. It may be permitted to me to mention, also, that 
while Dr. Huggins’s researches were still unannounced (or 
rather incomplete) I was so far fortunate as to indicate the 
possibility of employing the very method of research which 
Dr. Huggins was then engaged (unknown to me) in applying 
to Sirius. I propose here briefly to describe and explain the 
method, referring the reader who desires fuller information on 
these preliminary points to the paper of October 1868, men- 
tioned above. I am the more desirous of doing this, because I 
find the principle of the method not readily grasped, and that 
I conceive the explanation I am about to offer* may remove 
certain difficulties not uncommonly experienced. 
Conceive that a person, standing on the edge of a steadily- 
flowing stream, throws corks into it at regular intervals — say 
one cork per second. These would float down the stream, 
remaining always separated by a constant distance. Thus, if 
the stream were flowing three feet per second, the corks would 
be a yard apart (supposing, for convenience of illustration, 
that each cork was thrown with exactly the same force and in 
exactly the same direction). How, if a person a mile or so 
down the stream saw these corks thus floating past, he could 
infer that they had been thrown in at regular intervals ; and, 
moreover, if he knew the rate of the stream, and that the corks 
were thrown in by a person standing at the river’s edge, he 
would know that the interval between the throwing of suc- 
cessive corks was one second. But, vice versa , if he knew the 
rate of the stream, and that the corks were thrown in at inter- 
vals of one second, he could infer that the person throwing 
• I am indebted for the illustration on which is based the explanation 
which follows, to my friend and college contemporary, Mr. Baily, great- 
nephew of the eminent astronomer, Francis Baily. 
