316 Siluria—Present State of Geology. 
Much has been written on the metamorphic changes of 
rocks, but very unsatisfactory information has been arrived 
at. We still cannot tell how it happens that chalk, lime- 
stone, shale, sandstone, and coal, when traversed by gra- 
nites, porphyries, and trap rocks, are changed into crystalline 
limestone, siliceous slate, quartz, and coke, at one time ; and 
how, when in contact with the same Plutonian and trap rocks 
at another, produce no effect whatever. 
We regret much we have not space in the present number 
of our Journal to give an outline of the novelties Sir Ro- 
derick has introduced into his new work, entitled Siluria—a 
most elaborate work, which consists of 523 pages, containing 
163 woodcuts, 37 plates, and 2 maps. It is a faithful out- 
line of Sir Roderick’s previous labours, with a detailed de- 
scription and condensed practical popular view of the older 
sedimentary rocks, and their characteristic organic remains, 
including all the most recent information on this subject. 
It is to the protozoic series of former accumulations, and 
the creatures entombed in them, that Sir Roderick’s atten- 
tion is more particularly directed. Sir Roderick brings out, 
with very strong and conclusive evidence, that the Silurian 
System is an independent system, a system that appears 
to have been formed in various parts of the globe at one 
and the same time, formed of the same rocks and mine- 
rals, and inhabited by the same animals and plants; and 
Sir Roderick maintains that the animals and plants found 
in the Silurian strata of the different quarters of the globe 
are not only analogous, but identical.* We are in want 
of sufficient data to enable us to say much in regard to 
the meteorology and hydrology of that early period. The 
higher temperature, which must have then prevailed all 
over the globe, appears to have been derived from the 
internal heat, and not the solar heat. We learn from 
the late paleontological researches, that nearly one hundred 
species of fossils are common to the lower and upper divi- 
————— 
* Such a conclusion cannot be held as correct, until we have acquired more 
accurate data of the biological character of the different epochs, as well as the 
local faunz of the periods, 
