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characters are, however, associated with such a “ diversity of details” as to 
demonstrate that Pterodactyles must be placed in a new group, of equal 
value with birds, and called Ornithosauria. It is impossible to be perfectly 
convinced that Mr. Seeley is right in the conclusion he so firmly lays down, 
for, after all, it is based very much on analogy, and on the supposition that 
the vague laws of correlation are without exception. But as we know that 
the law of correlation is occasionally a deceptive guide, it is possible that it 
may be uncertain even in Mr. Seeley’s case, and that, after all, the Ptero- 
dactyle may have been a true reptile. If it is to be regarded as an avian- 
reptile, then the conformation of its organs of flight is in itself so wide a 
departure from the law of correlation as to throw considerable doubts on 
Mr. Seeley’s notion. Still it must be confessed that the author has brought 
to bear on his theory a mass of evidence of the weightiest kind, and that he 
has studied the group very deeply, and under the immense advantages which 
the Wood wardian Museum offers ; and hence we should be cautious even in 
exhibiting our scepticism. Whatever view may be taken of Mr. Seeley’s 
doctrine, his book must be regarded as an admirable work of reference, 
ample in its details, and well arranged as to its bibliographical information. 
Its plates are numerous, but are, we must say, rather badly drawn and 
“ smudgily” printed. 
THE FUEL OF THE SUN.* 
T HERE is nothing, politicians tell us, like a healthy opposition, and we 
think that this is as true of the world of science as it is of politics. 
The author of the present work does not sit on the “ Treasury Benches ” in 
Science. He is nothing if not heterodox ; but it gives us pleasure to say 
that his heterodoxy is of the best kind, it is calm, learned, and philosophic. 
If Mr. W. M. Williams differs in his opinion of the universe from the leading 
astronomers of the present day, he does so so modestly, with such good 
taste, and with such a proper display of the knowledge of his subject, that 
we are bound to listen to him respectfully and with attention. His book is 
not a 8 mall one, and it deals with a multiplicity of complex questions con- 
cerning the constitution of the sun and the existence of an universal atmo- 
sphere, and it would be out of our power to attempt here to grapple with 
views which we believe to be unsound and based on an insufficient practical 
study of the subject. Strange as it may seem, knowledge of natural 
phenomena, such knowledge as will enable the student to form correct 
opinions, cannot be obtained from books. There are little facts, small points 
in observation, which always incline the scale to this side or that, and which 
cannot be put down in words ; nothing but practical work and research can 
enable the student to realise and appreciate them, and it is thes«e which not 
seldom help him to conclusions. This knowledge it does not appear to us 
that Mr. Williams possesses, and for this reason we think he would have 
done better hod he not published th& present treatise. His ideas on the 
* “The Fuel of the Sun.” By W. Matthieu Williams, F.C.S. London: 
Simpkin A Marshall, 1870. 
