360 
then the sea, stratification, coral ; and lastly earthquakes 
and volcanoes. 
Now this is just right. Physical Geography ought to 
contain the dynamics of geology, and not be a mere 
description of the physical condition of the globe. A 
description of the plateaus and primary mountain chains, 
and secondary mountain chains, and plains and river 
systems of all the countries in the world, and distribution 
of birds, beasts, and fishes, used to be what was called phy- 
sical geography: and init the dynamical element, all idea 
of change and progress was almost entirely left out. All this 
description constitutes geographical knowledge, but is of 
the nature of information pure and simple, and has abso- 
lutely no value in education except as an exercise in 
memory, and as a basis for reasoning, supposing that this 
reasoning is ever superposed. But what Prof. Geikie gives 
us is the very life and soul of geological science, observa- 
tion on what the natural forces around us are doing, infor- 
mation as to what they are doing of the like kind elsewhere, 
and reasoning on the effect of these forces. It is a book 
which will at once rouse the curiosity of a child, and 
train it as far as it goes in sound scientific method. 
It is admirably adapted to be a reading book in 
elementary schools, and it is much to be hoped that 
it will be largely used. But for this purpose a cheaper 
edition ought to be published, J. M. W. 
OUR BOOK SHELF 
Exalted States of the Nervous System. By R. H. 
Collyer, M.D. (H. Renshaw.) 
Ir can only be with a feeling of regret that anyone can see 
so many pages, nearly 150, occupied with matter and 
arguments most of which had much better have been re- 
tained only among the oral traditions of the author’s ac- 
quaintances, for by publishing them he lays himself open 
to the severe criticisms of a non-appreciating scientific 
public. That Dr. Collyer was among the first to propose 
and employ anzesthetics, we will not question, but he 
cannot expect to increase the number of his supporters by 
the publication of such a work as the above, in which his 
want of knowledge of the first principles of scientific 
method and physiological fact is rendered too clear, An 
instance or two will suffice to indicate the manner in 
which the subject is treated. Speaking of chloral, he 
says—“ It is administered by the stomach. ... It seems 
that the action is immediate on the brain, through the 
eighth pair of nerves.” Thisis very different from the ex- 
planation of the discoverer of that substance, and quite 
contrary to any explanation of value that has been since 
proposed. The physiological dogma on which the author 
bases many of his arguments is that “the lungs at every 
respiration send vital electricity to the brain, which has 
been thus assimilated to subserve the purposes of life.” 
In a newspaper account of the relative chances of the 
Oxford and Cambridge crews for 1871, the author finds 
sufficient to justify the following valuable generalisation :— 
“thus endurance does not belong to mere size.” We think 
these quotations sufficient. 
The Botanists Pocket-book: containing in a tabulated 
form the chief characteristics of British plants. By 
W.R. Hayward. (Bell and Daldy, 1872.) 
A BOOK of modest pretensions, and not without its value. 
Asarule there is no class of scientific literature to be 
more carefully avoided than that which professes to com- 
press the whole of the elements of a science into a small 
portable volume; nowhere is the master’s hand more 
urgently required than in the compilation of text-books, 
NATURE 
| Mar. 13, 1873 
Mr. Hayward we do not recollect to have met with before 
as a botanical writer ; this little book, however, evidences 
great care in its preparation, and the author is careful not 
to claim for it too high a place, Its object is to “afford 
information to the tyro, and also to refresh the memory of 
the more advanced botanist who, by examining on the 
spot any doubtful plant, may be saved the trouble of 
carrying home specimens of little value ; it is not intended 
as a book for the study, nor as a rival to the many excel- 
lent and complete manuals of our leading botanists ; but 
to be accepted for what it is, viz., ‘A Botanist’s Pocket- 
book.’” This purpose it may well serve ; occupying not 
much over 200 pages of thin paper in limp cloth binding, 
it will be no great burden to the pocket or knapsack, and 
may frequently be usefully resorted to by a young botanist 
on the tramp, leaving more careful study till he gets 
home. A. W. B. 
LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions expressed 
by his correspondents, No notice is taken of anonymous 
communications. | 
Perception in the Lower Animals 
As several persons seem interested in Mr, Wallace’s suggestion 
that animals find their way home by recognising the odour of the 
places which they have passed whilst shut up, you may perhaps 
think the following little fact worth giving. Many years ago I 
was on a mail-coach, and as soon as we came to a public-house, 
the coachman pulled up for the fraction of a second. He did so 
when we came to a second public-house, and I then asked him 
the reason, He pointed to the off-hand wheeler, and said that 
she had been long completely blind, and she would stop at every 
place on the road at which she had before stopped. He had 
found by experience that less time was wasted by pulling up 
his team than by trying to drive her past the place, for 
she was contented with a momentary stop. After this I 
watched her, and it was evident that ‘she knew exactly, 
before the coachman began to pull up the other horses, every 
public-house on the road, for she had at some time stopped at 
all, I think there can be little doubt that this mare recognised 
all these houses by her sense of smell. With respect to cats, so 
many cases have been recorded of their returning from a con- 
siderable distance to their homes, after having been carried away 
Se SC Re: ee 
bd 
shut up in baskets, that I can hardly disbelieve them, though — 
these stories are disbelieved by some persons. Now, as far as I 
have observed, cats do not possess a very acute sense of smell, 
and they seem to discover their prey by eyesight and by hearing. 
This leads me to mention another trifling fact: I sent a riding- 
horse by railway from Kent vi@ Yarmouth, to Freshwater Bay, 
in the Isle of Wight. On the first day that I rode eastward, my 
horse, when I turned to go home, was very unwilling to return to- 
wardshisstable, and he several timesturned round. This led me to 
make repeated trials, and every time that I slackened the reins, 
he turned sharply round and began to trot to the eastward by a 
little north, which was nearly in the direction of his home in 
Kent. I had ridden this horse daily for several years, and he 
had never before behaved in this manner. My impression was 
that he somehow knew the direction whence he had been brought. 
I should state that the last stage from Yarmouth to Fresh- 
water is almost due south, and along this road he had been 
ridden by my groom ; but he never once showed any wish to 
return in this direction, I had purchased this horse several years 
before from a gentleman in my own neighbourhood, who had 
possessed him for a considerable time. Nevertheless it is possible, 
though far from probable, that the horse may have been born in 
the Isle of Wight. Even if we grant to animals a sense of the 
points of the compass, of which there is no evidence, how can 
we account, for instance, for the turtles which formerly congre- 
gated in multitudes, only at one season of the year, on the shores 
of the Isle of Ascension, finding their way to that speck of land 
in the midst of the great Atlantic Ocean ? 
CHARLES DARWIN 
The Sense of Smell in Animals 
THE hypothesis put forward by Mr. Wallace in NATURE of 
the 2oth ult., to explain the power possessed by some animals of 
a 
; 
— 
as 
