Bibliographical Notices. 259 



tion. The inferences derived from the study of meteorites are not 

 without interest ; since, in truth, these bodies seem to be messen- 

 gers sent direct from Kosmos. 



Chapters III. to VIII. inclusive deal with the rocks from a litho- 

 logical and petrological point of view. Dismissing the subject of 

 chemistry with extreme briefness, and not entering into that of 

 crystallography at all, the author details (1) the mineral substances 

 which constitute the aqueous rocks, and (2) those which form the 

 igneoxis rod's, in a series of very useful tables. The principal rock- 

 forming minerals are divided into family groups, which have a 

 certain naturalness, although such grouping might not in all cases 

 suit a fastidious mineralogist. 



Next comes the "nature and origin of crystalline and igneous rocks," 

 and the " nature, composition, and origin of water-formed rocks." 

 In dealing with the first Prof. Seeley adopts what may be termed the 

 views of the metamorphic school ; but when he speaks of the easy 

 solubility of carbonate of lime in heated water as one of the 

 agents of such changes he appears to have left out the carbonic 

 acid. In a somewhat similar way he tells us that " clay, slate, 

 gneiss, granite, felstone, rhyolites may exist simultaneously as 

 different conditions of the same rock." There are not many clays 

 that would make a rhyolite, we apprehend, without more of the 

 solid protoxide bases than usually belongs to clays. The primary 

 divisions of Basic and Acidic are artificial, but convenient. He 

 divides all igneous rocks into those which contain orthoclase and 

 those which contain plagioclase, further subdividing each into 

 quartz-bearing and quartz- free. Under this arrangement theolivine- 

 enstatite rocks or peridotites would seem to have no location. The 

 author is disposed to believe that the materials of igneous rocks were 

 originally the materials of stratified formations : the sorting power 

 of water gives a different composition to every mile of a formation 

 as it recedes from the shore. When all this was melted up the 

 parts nearest the laud would yield acidic rocks, the parts more dis- 

 tant from land would form the so-called basic rocks. Previously 

 (p. 35) he was disposed to regard the separation as in part 

 effected by the solvent action of water. Doubtless both causes may 

 exercise an influence in bringing about this singular result, for which 

 Durocher was obliged to suppose two separate magmas. 



Coming now to the water-formed rocks, Prof. Seeley says that 

 clay has very nearly the same composition as the mineral felspar. 

 Surely not ! The alkalis have in the main been removed. This is 

 a most important difference, and one which bears upon the questions 

 previously discussed. Kaolin rather than felspar must be regarded 

 as the basis of most clays. Under the head of Limestones the 

 author states that the oolite of the Secondary rocks was due to 

 evaporation at the surface of the sea, so that a film was formed 

 round some shell-fragment, which continued to increase in size as 

 it fell through the water till it sank to the bottom. This expla- 

 nation, be says, will also account for the uniform size of the grains 

 in the same stratum. As a rule, the amount of calcium salts in the 



