January 14, 1897 ] 
NATURE 
235 
be applied in search for special knowledge, and these ten 
stars are now indicated for that purpose.” 
The next cases are those afforded by the variability of 
stars in some globular star-clusters recently photographed 
at Arequipa with the 13-inch Boyden telescope. An 
extraordinary number of variable stars was discovered. 
The Harvard Circular, No. 2,' states ;— 
“At least eighty-seven of the stars in the cluster M 3 
(N.G.C. 5272), in Canes Venatici, have been found to be 
variable, and in some cases the change of light amounts 
to two magnitudes or more. In the cluster M 5 (N.G.C. 
5904), forty-six variables were found, out of 750 stars ex- 
amined, so that they form about 6 per cent. of the whole ; 
of the sixteen stars, contained in a circle 110” in diameter, 
six are variable. Smaller numbers of variables have been 
found in other clusters, but in other cases not a single 
variable has been detected out of the hundreds of stars 
which have been photographed ; the conditions of the 
search, however, not taking account of long period 
changes. In general, no variables have been found within 
about one minute from the centres of the clusters, on 
account of the closeness of the stars, and none are more 
than ten minutes distant from the centres. Some of the 
newly-discovered variables have short periods, in some 
cases of only a few hours. Thus, five photographs of 
N.G.C. 5904, taken at intervals of an hour on July 1, 1895, 
give for the magnitude ofa star about three minutes of arc 
preceding the centre of the cluster, 14°3, 1375, 13°8, 1379, 
and 14°33; four plates, taken at similar intervals. on 
August 9, gave the’magnitudes 14°2, 14°6, 14°8, and 15:0.” 
A special investigation has since been made of the 
variables forming part of the cluster M-5 Serpentis, 
N.G.C. 5904 (Ast. Mach., 3354). Forty-five photo- 
graphs of this ‘cluster have been measured by Miss 
Leland, and the measures include the greater portion of 
the forty-six. variables previously discovered. The 
periods of these variables are in general very short, not 
exceeding a few hours. One of these, designated: No. 
18, which follows the centre of the cluster about 6’ and 
is south 5’, has a probable period of 11h. -7m. 52s., or 
0°4638 days. The coordinates of the light curve of this 
variable are as follows :— 
Days. \ Mag. Days. Mag. 
0'00 ie 13°50 - 0°25 14°73 
0°05 13°87 | 9739 13°73 
o'10 14°35 | 0°35 14°72 
O'15 oe 14°70 | o'40 14°65 
0°20 Bs 14°72 0°45 13°56 
It thus appears that the star remains about minimum 
brightness during half the period, while the maximum 
luminosity is of relatively short duration ; the decrease 
in light is rapid, but the rate of increase is still more 
rapid, as it should be. The succession of changes does 
not seem to correspond with those of any previously 
known class of variable stars.” 
Now, since the presence of real nebulous material in 
some star clusters is accepted by many authorities, there 
seems ground for ascribing the phenomena in the nebula 
of Orion and in the star clusters to the same cause, and 
in attributing them to mere star-like appearances due to 
collisions. A variability of the kind described extending 
over a few hours or a few days is to me unthinkable in a 
“star,” properly so-called, that is, a body like our sun, 
and I have no hesitation in expressing my firm conviction 
that such variability can only be simply and sufficiently 
explained by the cause assigned for it by the meteoritic 
hypothesis—a clashing together of streams of meteorites. 
If the evidence that the apparent stars are really denser 
and more disturbed meteoritic swarms is accepted, the 
view that the nebulae are gaseous must fall to the ground, 
because the denser material of the “stars” must be the 
1 Nature, November 28, 1895. 
NO. 1420, VOL. 55] 
2 Lbid., June 4, 1896. 
| 
same as that which was least dense, that is, sparse in the 
first instance. 
I am glad, finally, to be able to state that Dr. Roberts, 
to whose continuous activity and marvellous skill the world 
of science is so much indebted, in a paper read at the 
meeting of the British Association at Liverpool this year, 
stated his opinion that the origin of the various star- 
like condensations in the spiral nebulz is “ more probably” 
meteoritic than gaseous in its origin. The line of argu- 
ment which has led him to this conclusion will be 
gathered from the following brief analysis of his com- 
munication :— 
He draws attention to the remarkable groups, curves 
and lines of stars that are clearly shown upon a photo- 
graph of the sky in the constellation Auriga, which was 
taken with an exposure of the plate during ninety 
minutes. Some of them are constituted of bright stars of 
nearly equal mignitude ; some are of faint stars, also of 
nearly equal magnitude ; some are of both bright and 
faint stars,and there is much regularity in the spacing 
distance between the stars in the several groups. These 
appearances are persistently found upon all photographs 
taken with long exposures of the plates in any part of 
the sky where the stars are numerous, such as Cassiopeia 
and Argo. . 
“What explanation,’ he asks, “can be offered to 
account for the grouping of the stars other than the 
assertion that they were from the beginning so placed ?” 
He then brings forward the evidence furnished by ‘the 
spiral ‘nebulz similar to that I have given above, and 
which I brought together more’ than a year ago. ° ; 
He then goes on: 
“T would submit that the evidence, part of which has 
now been laid before us, is reasonably conclusive that 
some, if not many, of the stars which we see in’ curves 
and in groups strewn over the sky have been formed in 
the manner which I have pointed out. There are, besides 
this, other methods of stellar evolution pointed out on 
other photographs, such as condensations’ into stars of 
nebulz. which have not, at present, symmetrical struc- 
tures and of globular and annular nebule. . . . ; 
“The question will naturally present itself to us: If it 
be true that stars are evolved from’spiral and other forms 
of nebulosity, whence came. the nebulous’ matter? | We 
can answer with confidence that it exists very largely and 
over extensivé areas in many parts of the sky ; and that 
it exists there in. the form of gas, or, more probably as 
Prof. Norman Lockyer urges in his ‘Meteoritic Hyfo- 
thesis.’ of meteors or meteoric dust.” 
Dr. Roberts’ reference to my work is very encouraging, 
since there are few workers in science whose researches 
have so close a bearing on the views I have put forward. 
For my own part I feel that the totality of the observa- 
tions above recorded is all highly suggestive of meteoritic 
action, and I can only in conclusion express my belief 
that before very long as striking evidence of variability 
will be found in the stars in the spiral nebula, as the 
Harvard observers have obtained from the globular 
star clusters. J. NORMAN LOCKYER. 
THE THEORY OF SOLUTIONS. 
AS some recent v/va voce remarks of mine have re- 
ceived an interpretation more wide than I intended, 
I shall be glad to be allowed to explain that when (now 
several years ago) I became acquainted with the work of 
van t’ Hoff I was soon convinced of the great importance 
of the advances due to him and his followers... The sub- 
ject has been prejudiced by a good deal of careless 
phraseology, and this is probably the reason why some 
distinguished physicists and chemists have refused their 
adhesion. It must be admitted, further, that the argu- 
ments of van t’ Hoff are often insufficiently set out, and 
a 
