NOTICES OF BOOKS. 413 
knowledge, and are therefore of little practical benefit. In such specu- 
lative subjects, indeed, the views of matters of detail adopted by each 
writer, must depend on his views of the sequence and importance of 
geological events. Our author, for instance, considers it probable that 
a considerable number of evergreen trees indigenous in the Rhine valley 
are survivors from the miocene period,—a view which we think wholly 
untenable, if he means to imply that any part of the now-existing ve- 
getation has retained its position where it now grows since so remote 
an epoch. On the contrary, we believe that since the most recent ter- 
tiary period, the great refrigeration of our climate which must have 
accompanied the glacial epoch is quite incompatible with such a vege- 
tation, and that our whole flora, except a few alpine species, has pro- 
bably been introduced since that time. 
We are sorry to find, in a general work devoted to geological 
questions relative to the distribution of plants, no indications of an 
acquaintance with the very important labours of Lyell and Forbes. 
The masterly summary of the whole question by Sir Charles Lyell, in 
his ‘ Principles of Geology,’ is based upon a great accumulation of facts, 
and a complete knowledge of the amount of geological changes; while 
in the memoir by Professor Edward Forbes, on the vegetation of the 
glacial epoch, we have the application to a particular geological period 
of the author’s extensive knowledge of zoology and botany; and both 
these writers have treated the subject with so much completeness, that 
their papers may be considered the foundation of all accurate discus- 
sion on the subject. 
We regret also to observe a tendency, on the part of the author of 
the pamphlet before us, to place a degree of reliance on the identifica- 
tion of fossil species of plants with those now existing, which we do 
not by any means think the materials usually at the disposal of fossil 
botanists can warrant. Every one who is accustomed to the handling of 
. large masses of plants, must have felt the great difficulty of referring 
specimens without flowers or fruit to their Natural Orders. How much 
more difficult, then, must it be to identify fossil specimens, chiefly single 
leaves, with living species !—a thing now often done, with the utmost 
confidence, on exceedingly slender grounds. We should not like to be 
obliged to distinguish fragments of dried specimens of Pinus Pumilio from 
Pinus sylvestris, or from a great many other Pines; and yet our author 
tells us, on the authority of Góppert, that the former of these so-called 
