Geology. 233 



passes on to those of other countries. He then takes up the 

 volcanic rocks, and mentions the chief types of porphyries, 

 basalts, etc., used for building purposes in Europe. The sedi- 

 mentary rocks are treated in groups, according to the geologic 

 epoch to which they belong. In all cases the observations are 

 based especially on the material in the museum mentioned. The 

 particular value of the work is, therefore, strictly local, for stu- 

 dents in connection with the Cambridge collection ; but it may 

 occasionally prove of service as a book of reference for localities. 

 For its particular purpose the work appears well executed. 



l. v. P. 



3. Die Kontaktmetamorphose im Kristianiagebiet ; von V. 

 M. Goldschmidt. 8°, pp. 483, Videnskap. Skrift. 1. Mat. nat. v. 

 Kl. 1911, No. 1. — It would be a natural expectation that a trea- 

 tise on some phase of the geology of the Christiania region by 

 one of Prof. Brogger's pupils and assistants, and under his gen- 

 eral direction and advice, would be a notable contribution in the 

 particular field to which it is devoted. This expectation is fully 

 realized in the fine volume which is the subject of this notice, for 

 we hardly recall any work on the subject of contact metamorph- 

 ism which, based on a special locality, is of more general interest 

 and importance. While want of space forbids us from giving it 

 more than a general notice, the following features of the work 

 may be mentioned: 



The first part is devoted to a general geological description of 

 the contacts, those of the middle portion of the region being the 

 ones especially dealt with. After a general introduction a num- 

 ber of contact zones are described in full detail, and in this part 

 a number of contact ore deposits are also treated. 



The second part is given to the results of the petrographic 

 study of the contact rocks, and is enriched with a large number 

 of chemical analyses, which afford data for conclusions regarding 

 the petrogenesis of the different types. As features of general 

 interest some conclusions of the writer maybe mentioned: There 

 is no evidence of stress, of dynamic metamorphisra, in the rocks ; 

 the thickness of sedimentary cover was 1500 meters, giving a 

 static pressure of 420 kilos per cm 2 ; under this pressure coarse 

 granular hornfelses formed in the inner contact zone. The meta- 

 morphism took place without any melting of the sediments, as 

 shown in several ways ; and the author is inclined to think with- 

 out much action from solutions, or gases. The action in the main 

 took place before the solidification of the intruding magma. 

 The temperature of the inner zone was between 11 00° and. 1200° C; 

 in the outer zone, where amphibole occurs, not over 550°. The 

 author here points out that the use of quartz as a geologic 

 thermometer is not justified unless we know something in regard 

 to the pressure involved, for the inversion point between quartz 

 and tridymite must be greatly raised by it. The writer then 

 takes up the classification of the rocks and goes on to their con- 

 sideration from the standpoint of modern physical chemistry. 



Am. Jour. Sci. — Fourth Series, Vol. XXXII, No. 189. — September, 1911. 

 17 



