1872.] The Construction of the Heavens. 315 
Michell limited his attention to the lucid stars, not enun- 
ciating any complete theory respecting the galaxy. The 
most important of his theoretical views, or rather the most 
important of the facts which he established,* is that which 
relates to the existence of laws of arrangement (even among 
the stars visible to the naked eye), according to- which 
the stars form systems, separated from each other by rela- 
tively vacant spaces. ‘‘ We may conclude,” he says, ‘‘ that 
the stars are really collected together in clusters in some 
places, where they form a kind of systems; whilst in others 
there are either few or none of them, to whatever cause this 
may be owing, whether to their mutual gravitation or to 
some other law or appointment of the Creator. He then 
proceeds to inquire whether the sun “likewise makes one of 
some system.” He considers that this is probably the case, 
and he endeavours to separate those stars which probably 
belong to the same system as the sun from those which do 
not. ‘‘ There are some marks,” he says, ‘“‘ by which we 
may with great probability include some and exclude 
others,—while the rest remain more doubtful. Those stars 
which are found in clusters and surrounded with many 
others at a small distance from them, belong probably 
to other systems and not to ours. And those stars which 
are surrounded with nebule are probably only very great 
stars, which upon account of their superior magnitude 
are singly visible, whilst the others which compose the 
remaining parts of the same system are so small as to 
escape our sight. And those nebulz in which we can 
* Amongst the facts which Michell established must be included the 
existence of binary star systems. Nothing can be more complete or demon- 
strative than Michell’s reasoning on this subject; and I can conceive no 
reason why the credit of the discovery should be refused to the man who 
deduced it by exerting the noblest of human faculties—the power of abstra@& 
reasoning, in order that it should be handed over to another (however eminent) 
who deduced it from direct observation. It is true Michell failed to convince 
his contemporaries, and that his reasoning if it had not been subsequently 
confirmed by Sir W. Herschel’s observations might have remained to this day 
unappreciated, save by the few. But this does not do away with the fa@ that 
Michell’s demonstration was complete; and his credit ought not to be 
diminished because the many could not grasp the full value of the proof. A 
very slight extension of such a method of judging might deprive the Herschels 
in their turn of the credit now (as I think unjustly) assigned to them for the 
discovery, to make it over to the first person who (say) by obtaining photo- 
graphic records of double stars, should enable every one to see for himself that 
one component circles around the other. Surely the reputation of the 
Herschels does not require that any credit should be assigned to them which 
is justly due to another. Michell has indeed been particularly unfortunate in 
such matters, since, to mention no other instances, the so-called Cavendish 
experiment for weighing the earth was not only devised by him, but the very 
instrument with which Cavendish conducted the experiment was constructed 
‘under Michell’s superintendence. 
