570 Reviews — LyelVs Principles of Geology. 



recent eruption in the Gulf of Santorin in February, 1866 ; as also 

 of the earthquake in New Zealand in 1855, and the permanent up- 

 heaval and subsidence of land in that archipelago, is given on the 

 authority of Messrs. Eoberts, Walter Mantell, and F. A. Weld. A 

 new fault or shift of 9 feet in the rock is described, and a map of 

 the region convulsed by the earthquake is appended. 



In reference to the earthquakes in Calabria in 1783 and 1857, the 

 origin and mode of the propagation of earthquake waves, is treated 

 of and illustrated by several new diagrams (p. 135 to 140). Some 

 account is also given of Mr. Eobert Mallet's prf)posed method of cal- 

 culating mathematically the depth of the earth's crust from which 

 the shocks may proceed. 



At p. 192, we have the observations of Messrs. Gwyn, Jeffreys, 

 and Torell on Shells of the Glacial Period in the Udde valla district 

 in Sweden. 



In chapters 32 and 33, the old notion, that the crystalline rocks, 

 whether stratified or unstratified, such as granite and gneiss, were pro- 

 duced in the lower part of the earth's crust at the expense of a 

 central nucleus cooling from a state of fusion, is shown to be un- 

 tenable, since granite is found to be of all ages, and the metamorphic 

 rocks to be altered sedimentary deposits, implying the denudation of 

 a previously solidified crust. Also, that the latest chemical observa- 

 tions on the products of recent eruptions favour the doctrine, that 

 large bodies of salt water gain access, during an eruption, to the 

 volcanic foci. And lastly, that the reservoirs of melted matter in 

 the interior, though vast, may hold only a very subordinate place in 

 the earth's crust. 



The heat supposed to be continually lost by the planet by radiation 

 into space, may perhaps, it is suggested, be restored by solar mag- 

 netism in connection with electricity and chemical action. 



In the 35th chapter, the objections originally urged against 

 Lamarck's theory of transmutation and his replies are considered. 

 Also the question whether, if new species are created from time to 

 time, their first appearance would have been witnessed by the 

 naturalist. Kemarks are offered on the "Vestiges of Creation," and 

 on the theory of " Natural Selection," as advocated by Dr. Darwin 

 and Mr. A. Wallace. The change of opinion produced by Dr. 

 Darwin's work on " The Origin of Species," is pointed out, and Dr. 

 Hooker's views on the formation of species in the vegetable world 

 by variation and selection are noticed. 



The 36th chapter contains an explanation of Mr. Darwin's views 

 on the formation of new races by selection, both unconscious and 

 methodical, whether of plants or animals under domestication. His 

 doctrine of "Pangenesis," or the manner in which long lost charac- 

 ters may be revived in the offspring of cross-breeds, is also alluded 

 to. Likewise the fact that certain parts of animals or plants may 

 be made to vary by selection, while other parts of the same remain 

 unaltered. The hybridisation of plants and animals is also con- 

 sidered in its bearing on the nature and origin of species. 



The 37th chapter treats of natural as compared to artificial 



