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POPULAR SCIENCE REVIEW. 
over some fifty-eight degrees in length and about thirteen 
degrees in breadth. 
But it is when we consider the stars down to the fifth magni- 
tude inclusive that we first begin to recognise the existence of 
a marked tendency to stream-formation. It is among these 
stars, in fact, that we find those streams which the ancients 
recognised when they gave to certain star-groupings such 
names as Hydra, Draco, Serpens, the River Eridamus, and when 
they marked down among the constellation-pictures two streams 
from the water-can of Aquarius and a band connecting to- 
gether the two fishes. The prolongations of some of these 
streams of lucid stars have been recognised by those modern 
astronomers who gave to certain southern star-groupings the 
names Hydrus, Reticulum, and the like. 
Now, the chief question which has to be answered, in con- 
sidering the evidences of stream-formation, is whether the 
streams are apparent only or real ; and, in order to answer 
this question, we have to inquire what form or degree of stream- 
iness (so to speak) might be expected among the 1,500 
stars, down to the fifth magnitude inclusive, if these were 
really spread at random over the celestial sphere. In the 
“Popular Science Review ” for July 1870, I have indicated the 
means whereby I have tested this matter, and the conclusion 
to which I have been led — this namely, that although among 
1,500 or 2,000 points distributed at random over a surface of 
any kind, certain groups resembling streams might be recog- 
nised, such streams would not be nearly so well marked as the 
streams actually observed among the stars down to the fifth 
magnitude. But, on the other hand, it is not to be expected 
that the star streams actually recognised should be so exceed- 
ingly well marked and regular, or should be traceable over 
such great distances, that the reality of the stream-formation 
must be obvious at once. Had this been the case, indeed, the 
reasoning by which I have endeavoured to establish the reality 
of the phenomenon would not have been required. The first 
astronomers would have recognised the phenomenon as clearly 
as we can do. Therefore I do not consider the arguments 
which have been chiefly urged against these streams of lucid 
stars, regarded as having a real existence, as needing refutation. 
It has been urged that the streams can only be traced over 
such and such distances; that they can be carried this way or 
that, according to fancy, and so on. This, however, was to be 
expected ; if it were otherwise, the reality of the streams would 
long since have been recognised ; and apart from this, re- 
membering that we are looking into the depths of space, and 
that, supposing star streams really to exist, we must see them 
foreshortened — in many instances projected on a background of 
