390 sosMAN AND merwin: data on palisade diabase 



stone and shale, apparently continuous with the floated slab, were 

 obtained. 



A preliminary experiment, made by heating specimens of the 

 diabase and the arkose ^ide by side in a platinum crucible, showed 

 that at a temperature where the diabase would flow readily, the 

 sedimentary rock was also partly fused, altho in the original in- 

 clusion there was no indication of fusion. The authors there- 

 fore undertook, as a side issue to the main question of the volume 

 relations, a brief study of the relative fusing temperatures of 

 the rocks in question. The results, while necessarily incomplete 

 because of the complexity of the rocks and the unknown factors 

 involved, show that the temperature at which the diabase was 

 intruded must have been considerably lower than the temperature 

 necessary to liquefy this . diabase in the laboratory. This fact 

 has long been suspected, altho there has been hitherto very 

 little quantitative evidence bearing on the question.^ 



The diabase. There is no published analysis of the rock from 

 this particular locality, but the rock is very similar to the ''basal- 

 tic diabase" in the near-by railroad tunnels thru the Palisade sill, 

 and to that of Rocky Hill.^ Mr. Hostetter's determinations on 

 our specimen gave 0.6 per cent water at 105°, 8.74 per cent FeO, 

 and 1.51 per cent Fe203. The character of the rock would be 

 approximately represented by the following weight percentage 

 composition: SiOs 51, AI2O3 13, CaO 10.5, MgO 7.5, FeO 8.5, 

 Fe203 1.5, alkalies 3.5, Ti02 1., water and miscellaneous 1.5. 

 Its density at 20° was 2.97. 



The rock is fine grained, and consists of a dense holocrystalline 

 mass of feldspar and augite, with phenocrysts of pyroxene and 

 of plagioclase feldspar. Minor minerals are biotite, magnetite, 

 and occasional olivine. 



Fusion of the diabase. The tests were made by placing small 

 fragments of the rock, wrapped in platinum foil, in an electrically 

 heated furnace held at a constant known temperature, measured 

 by a thermoelement and potentiometer. After exposure to this 



' See F. E. Wright, Intrusive Rocks of Mt. Bohemia, Geol. Surv. Michigan, 

 Ann. Rep., 1908, p. 391. 



* Geol. Surv. New Jersey, Ann. Rep., 1907, p. 121, analysis 4, 5, and 12; and 

 pi. 16. Description, pp. 126-128. 



