and Rock Densities at High Temperatures. 35 



of certain granites "* a large number of instances in which it is 

 believed that a basic intrusive has assimilated acid rocks along 

 its contacts. The shattering of a siliceous rock by the quartz 

 inversion, and the penetrating power of liquid diabase and 

 diopside, which we have noted above, lend additional plausi- 

 bility to Daly's view of the phenomena. 



Diabase and sandstone. — Returning now to the question of 

 the "floated" sandstone and shale slabs described by Lewis 

 (see p. 25) our experimental data again find application. A 



Fig. 11. 



A3 





hU:Kn;:i^p-(. 



io ; n 







Fig. 11. Diagrammatic sketch of the contact of the trap and underlying 

 shale at the base of the cliff at Linwood, on the Palisades. (After Kiimmel.) 



fragment of pure quartzite without pore spaces would have at 

 1150° a kilogram-volume of about 395, supposing it not to 

 have inverted to tridymite or cristobalite. Diabase glass at 

 1150° would have a volume of 384. The quartzite would be, 

 therefore, 2*9 per cent lighter than the fused diabase, and 

 would float up in it, if free to move. 



The arkosic sandstone which forms the majority of the 

 inclusions in the Palisade diabase consists chiefly of quartz and 

 orthoclase. Extrapolation of our curve for orthoclase (see p. 

 33) would give it a volume at 1150° of about 404. The aver- 

 age volume of the arkose (about one-third quartz and two- 

 thirds feldspar), would therefore be 400 at 1150°, or 4'2 per 

 cent lighter than the liquid diabase. Loose slabs of the arkose 

 would therefore tend to float up into the diabase sheet. 



Such floating due to normal gravitative adjustment would 

 seem to offer the simplest explanation of the frequent occur- 

 rence of slabs of the underlying rock found in various positions 

 in the Palisade sheet. A good example is seen in the sketch 

 *E. A. Daly, this Journal, xx, 185-216, 1905. 



