\ 
1878. ] 341 [Chase. 
sulphur. The light shed by it was pulsating and sufficiently powerful 
to light up the Tennessee shore and the sand bars, so as to show every log 
and stump.” 
PROBABLE INFERENCES. 
1. The number of stone-falls and detonating meteors observed on the 
11th, 12th, and 13th of November is more than double the average daily 
fall. Hence the periodic return of a cluster whose orbit intersects that of 
the earth is rendered highly probable. 
2. None of the aerolites or meteors of the preceding list are known to 
have been conformable to the radiant in Leo, while those of November 
13th, 1835 and November 12th, 1877, were certainly wn-conformable ; their 
heliocentric motion having been direct. This aerolitic group cannot there- 
fore be connected with the shooting stars of November 14th. 
3. These facts, it must be confessed, are unfavorable to the hypothesis, 
formerly advocated by the writer, that ‘‘ meteoric stones are but the largest 
masses in the nebulous rings from which showers of shooting stars are de- 
rived.’’* It is true that in the great star showers of 1799, 1833 and 1866 a 
number of large fire-balls were seen which belonged undoubtedly to the 
cluster of Leonids ; but it is remarkable that among all this number no de- 
tonation was ever heard, and that no meteoric stones have ever fallen 
during these extraordinary star showers. 
A. The dates of the phenomena given above indicate a period of seven 
years. Several sporadic fire-balls, however, have appeared at this epoch, 
and no definite conclusion in regard to the period is possible without addi- 
tional data. 
Criteria of the Nebular Hypothesis. 
By Purny Earue CuHaset, LL.D., 
PROFESSOR OF PHILOSOPHY IN HAVERFORD COLLEGE. 
(Read before the American Philosophical Society, March 1, 1878.) 
The views of astronomers, respecting the mode of action in world-build- 
ing, have been various and vague. No one appears to have put upon te- 
cord any numerical calculations, undertaken with a view crucially to test 
the nebular hypothesis, or any suggestions as to the proper way to make 
such calculations. 
Statements have been made, at different times, by investigators who 
thought that observed velocities might be explained by the results of nebu- 
lar condensation, but no one, except Ennis,+ has given us any means of 
judging on what grounds the belief rested. It seems probable that they 
all regarded the formation of planetary rings as confined to the superficial 
* Meteoric Astronomy, p. 64. 
+ “Origin of the Stars;” L., E. & D. Phil. Mag. April, 1877. 
