ASTRONOMY: C.P.OLIVIER 
47 
and percolation are represented by only about 30% as against 50% 
of that volume. As stated above, it remains to be determined by the 
observations of many future years whether there is a tendency to a 
normal variation in annual rainfall upon the Isthmus, as seems to be 
suggested by the figures already of record. 
^ In a paper which appeared in Professional Memoirs, Corps of Engineers, U.S.A., for 
November-December, 1915. 
THE METEOR SYSTEM OF PONS-WINNECKE'S COMET 
By Charles P. Olivier 
LEANDER McCORMICK OBSERVATORY. UNIVERSITY OF VIRGINIA 
Communicated by E. W. Morley and read before the Academy, November 14, 1916 
The National Academy of Sciences, by two grants from the J. Law- 
rence Smith Fund, having been the means of greatly extending the mem- 
bership and work of the American Meteor Society, it seems well to report 
to the Academy the most interesting single result of the work so far 
obtained. 
Late in May and early in June of this year two of our observers, 
Mr. John Koep and Mr. Philip Trudelle, both of Chippewa Falls, Wis., 
sent in a series of observations which showed that meteors were at least 
three times as numerous as is usual for the time of the year mentioned. 
This attracted immediate attention and the observations were worked 
up without delay. The orbits, which corresponded to the positions 
found for the radiants, were then computed. As several of the orbits 
turned out to have the same elements, a search was next made to see 
if any of the known comets had a similar orbit. 
At once it was seen that Pons-Winnecke's Comet fulfilled the condi- 
tions excellently and there was no doubt that the meteors and the comet 
had a common origin, and, that another case of the connection between 
a meteor stream and a comet had been found. 
The first orbits for the meteors had been computed on the usual 
assumption that they moved with a parabolic velocity, but there were 
obvious reasons to show that this was only a first approximation. 
The orbits were then all computed as elliptical, assuming their major 
axes equal to that of the comet. This set made a far better agreement 
with the elements of the comet's orbit and put the connection beyond 
question. 
Before speaking further about the meteors themselves, it will be of 
interest to review briefly the history of this rather remarkable comet. 
Discovered by Pons in 1819, no further observations were obtained until 
