REVIEWS. 
117 
vince towards its confines. Out of the many hundreds of land-moUusks 
inhabiting the Caucasian province at its specific centre, only ninety have 
reached the British Isles ; of which thirty- five stop short of Scotland, and 
nineteen in Ireland. Their pro^^ress northwards, it may be argued, is 
arrested, to a great extent, by a change of climate, and in all directions by 
foes, by mountain-barriers, by rivers, and by other physical and unknown 
causes. It will readily be conceded that laud-species have greater facilities 
of locomotion than freshwater species especially inhabiting stagnant ponds 
and ditches ; and it should follow, according to the doctrine of migration, 
that the further off freshwater species are from the specific centre of a pro- 
vince, the more diminished in number than land-species they would be. 
The very contrary is the fact ; out of five hundred and sixty species of 
Helix inhabiting the Caucasian province, a very large proportion of which 
are assembled at its specific centre, we have but twenty-four in Britain, of 
which only eleven range throughout. The disproportion in the number of 
Clausilia is larger still. This genus is especially .populous at its specific 
centre. Between two and three hundred species inhabit Austria and 
Hungary, yet we have but four in Britain, of which only one ranges 
throughout. Let us now turn to the sluggish mud-dwelling Lymnajacea of 
the ponds and ditches of the province. There are not six species, it may 
be safely stated, in all Europe more than there are in Britain. They have 
no particular centre of creation. There is no evidence to show whether 
the alleged primogenitors of our British species were created in Siberia, 
Hungary, or Thibet. There is scarcely any variation, either in the form 
or number of the species in those remote localities." 
The other topics are equally well discussed, and valuable facts brought to 
bear upon them ; and altogether, although the arguments are very concisely 
stated, we have very valuable considerations very lucidly put. A complete 
bibliographical list and an excellent index complete this useful volume, which 
will doubtless, and deservedly, find a proper place in most naturalists' 
libraries. 
Year Book of Facts, 18(}3. By John Timbs, F.S.A. 
London : Lockwood and Co. 1863. 
Every year Mr. Timbs issues, and we receive, a ' Book of Facts.' These 
are not, however, Mr. Timbs's facts, but the property of numerous people. 
The book is, as is well known, a series of cuttings from various publica- 
tions, but not the less a useful book that it is composed of the " pickings" 
of wise men's brains. If we cannot always depend on the judgment and 
knowledge of the compiler, as displayed in his selections, or if we should 
think him a little too much attached to certain publications, and a little 
oblivious of or antagonistic towards others, he at least is not altogether un- 
amicable, for he shows his partiality by naming and praising his favourites, 
and with respect to the rest, merely uses their matter, and consigns to 
oblivion their names and their fames. In the present volume the materials 
are beyond the average value of Mr. Timbs's former year-books ; and be- 
sides the section devoted specially to Geology, there are scattered articles 
in various other portions interesting to geologists, such as the " origin of 
petroleum," " machine for cutting coal worked by compressed air," " Ran- 
some's artificial stone," coal "and iron of South Yorkshire," "artesian 
wells," " secular cooling of the earth," and " the relations between earth- 
quakes and magnetic disturbances." 
