STAR STREAMS AND STAR SPRAYS. 
399 
Unfortunately we have no means of modifying the conditions 
of the problem presented to us by the stars. We must be 
content to analyse patiently the evidence by means of which 
alone the problem can be attacked. Whether when that has 
been done, or while that is being done, we shall be able to form 
clear and definite conclusions respecting the stellar system, need 
not at present concern us. It is at any rate certain that if the 
secret of the heavens is to be disclosed, it can only be as the 
result of systematic inquiries directed to the vast mass of 
information which has already been gathered together ; and the 
doubts we may entertain as to the actual fruits of such inquiries 
ought not to deter us from making them, since that would 
be in effect to give up the problem of the star-depths altogether. 
To use the words of the astronomer to whom more than to any 
other, save one alone, we owe the power itself of making such 
inquiries, we must 44 not be deterred from dwelling consecutively 
and closely on speculative views by any idea of their hopeless- 
ness which the objectors against 4 paper astronomy ’ may 
entertain, or by the real slenderness of the material threads out 
of which any connected theory of the universe (at present) has 
to be formed. Hypotheses ftngo in this stage of our knowledge 
is quite as good a motto as Newton’s non Jingo , provided 
always they be not hypotheses as to modes of physical action 
for which experience gives no warrant.”* 
My purpose in the present paper is to pursue an inquiry 
(commenced by me some five years ago) into a certain pecu- 
liarity of the arrangement of objects within the star-depths, 
which appears to promise some insight into the real laws of 
stellar aggregation. I refer to the circumstance that there 
may be observed among the stars a tendency to arrangement 
in streams, of greater or less length, and more or less distinctly 
recognisable. I offer at present no explanation of the observed 
fact, but seek rather to convince the reader that this peculiarity 
has a real existence, and that it may be regarded as in fact a 
characteristic peculiarity of the stellar system. It must be 
mentioned, however, that the tendency to stream-formation 
among the stars is not to be regarded as universal. On the 
contrary, it is but a sign of a much more general law, accord- 
ing to which the stars are found to aggregate in certain regions 
and to be segregated from others, as though, in some long past 
era, forces had been at work which drew the star material 
towards certain regions of space, to the avoidance of others. 
And here again, I would invite attention to the fact that the 
study of these laws of stellar aggregation and segregation seems 
to afford the only means of attacking a problem of immense 
From a letter to the present writer, August, 1869. 
