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POPULAR SCIENCE REVIEW. 
be easily determined, and the author has avoided giving a detailed account 
of the numerous minute variations to which some of his favourites are sub- 
ject, and has done wisely, as we think ; but we cannot approve of his 
remarks on this subject, which would seem to convey to his readers that 
these minute distinctions are absolutely needless, whereas to a great extent 
they are only needless for his purpose. In other respects Mr. Heath’s book 
is so good that we are sorry to see him making statements ad captandum 
vulgus. We would also suggest as an improvement to this section of the 
book the addition of a synopsis of the genera ; at present the generic and 
specific characters are combined in the descriptions, and perhaps this 
arrangement may be retained with advantage ; but such a statement of the 
characters of the genera as would enable the reader to understand what is 
meant by a genus, and what is the significance of the scientific names 
employed, would certainly place the work on a much higher footing. The 
descriptions are well illustrated by coloured figures of each species (generally 
reduced in size), produced by a photo-lithographic process from the objects 
themselves ; they are generally well executed and very characteristic. 
PHYSIOGRAPHY. * 
I T needed very little of the prophetic spirit to foresee that the introduc- 
tion of physiography into the syllabus of the Science and Art Depart- 
ment would be speedily followed by the publication of text-books of 
physiography. Dr. Mackay is first in the field, and as an experienced hand 
at geographical compilation, he has succeeded in producing a neat little work, 
which may be found useful to students who think of facing the May 
examinations at South Kensington. Whether any good will result from the 
substitution of physiography for physical geography, is quite another 
matter, with which Dr. Mackay has of course nothing whatever to do. It 
is believed by very high authorities that physiography, or the science of 
nature in general, offers the best means of introducing young people to a 
little knowledge of geology, biology, physics, chemistry, astronomy, and 
what not. But it must also be acknowledged that so comprehensive a 
subject can be mastered only by one who commands a good deal of 
scientific knowledge. Physiography is indeed, in one sense, the sum 
and substance of all natural science, though in another sense it may be 
regarded as the starting point of the scientific circle. With so much 
matter to compress into so little space, we are surprised to find that 
Dr. Mackay has a good deal to say about the Great Pyramids, and that he 
should think it worth while to advocate the use of the ancient sacred cubit 
against what he calls “ the much vaunted French metre.” But our sur- 
prise culminates when we find him going out of his way to explain how a 
change in the inclination of the earth’s axis might have brought about the 
Noachian deluge, and have indirectly affected the longevity of man ! 
• “ Physiography and Physical Geography.” By the Rev. Alex. Mackay, 
LL.I)., F.R.G.S. Small 8vo. Edinburgh and London: Blackwood & Sons. 
1877. 
u Physiography : an Introduction to the Study of Nature.” By T. H. 
Huxley, F.R.S. Small 8vo. London : Macmillan. 1877. 
