a 
Kirkwood.] 264 (Oct. 5, 
ered by Encke may be regarded with much probability as the effect of a 
similar cause. * 
The recent able and noteworthy papers of General Parmentier,} of 
Paris, and Dr. Meyer, { of Geneva, have invested these older discussions 
of the same subjects with fresh interest and importance. The actual dis- 
covery of chasms in the asteroid ring was the result of a previous theo- 
retical determination of the parts where void spaces would be produced 
by Jupiter’s influence. The definite claims of the writer then are : 
(1.) To have designated the theoretical positions of 
asteroids ; 
gaps in the zone of 
(2.) To have shown that these divisions actually exist; and 
(3.) To have first assigned a physical cause for the divis ons of Saturn’s 
ring. 
A restatement of the principal evidence, showing the harmony of re- 
cent discoveries with the conclusions announced seventeen years since, is 
given below. The portions of the ring in which the periods would be 
commensurable with that of Jupiter are : 
1, THe DISTANCE 3.2776. 
At this distance a planetary mass would make precisely two revolu- 
tions while Jupiter completes one. Hence, as has been frequently shown, 
a chasm in the ring would be the probable consequence of Jupiter’s dis- 
turbing influence. How far is this theoretical inference sustained by facts ? 
An examination of the table of distances shows 
POCWEOM CUSHING WCCO uve odin HN S ua Leica tel thevest Ov Baterolds 
bhp 8.200 HOU BBO Tie vs PT TKS et Female Ge Pinca ies puaieel tain bh 
nde 8.857 and 8:404.0 00004, Pinu ver eoneod vemtaseticesd Men ple Gk MaMa pal Oh iy 
That is, the part of the zone just within the distance at which a planet’s 
period would be one-half that of Jupiter, contains the extraordinary num- 
ber of thirty-seven minor planets, while the next space of equal breadth 
(that containing the distance 3.2776), is a total blank, not a single asteroid 
having yet been found within it. The exterior space immediately ad- 
jacent, and of the same extent, contains eight. The confirmation of the 
theory is thus most striking in precisely that part of the zone where we 
have most reason to expect it. 
II. THe DISTANCE 2.5012. 
ILere an asteroid’s period would be one-third that of Jupiter. The order 
of commensurability would be less simple, but the results of perturbation 
would be of the same nature. The part of the zone included between the 
distances 2.30 and 2.80 contains 143 minor planets; 45 within the critical 
*See Proc. A, A. A. S., 1866 and 1875; Met. Ast. Ch. xiii; Monthly Notice, R. 
A. §., Jan. 1869; Proce. A. P. 8., vol. xii, p. 163; Smithsonian Rep., 1876; London 
Observatory, July, 1882. 
t L’Astronomie, for 
{ Astr. Nach., No. 2 
», 1883, 
