1899] MICROSCOPICAL JOURNAL 293 



often get to it by trolleys or by walking. In O'Rourkes' 

 quarry there is the best development of trap crystals. 

 The silica is also in crystals, amethyst, smoke quarts 

 and calcedony and opal. When studying what looked like 

 a vein of quartz that is found in Orange I came across a 

 bed of clay that looks as if it had been washed down the 

 rocks from above. The apparent vein is perpendicular 

 and over a foot in diameter. It is pulverulent and through 

 it are the crystals of amethyst and smoke quartz. I 

 easily dug it out,as the quartz is pulverulent and crushes 

 in the hand. The quartz is deposited from solution in 

 water and then forms crystals of amethyst and other 

 things. The vein or fault being thus left open by the 

 forcing of the sides apart may be filled from below or 

 above. In this case it was not filled from above because 

 only a thin layer of gravel was there. It cannot be filled 

 from below by the forcing upward of the Newark sand- 

 stone for it contained different Bacillaria that are found 

 in other rock above or below. Now this clay, which was 

 stained reddish with iron, I dug out, took home, exam- 

 ined and washed it with ammonia in the usual manner. 

 In it were Synedra ulna, Melosira granulata and others 

 more scarce with spicules of Spongia. The Synedra and 

 Melosira were distinct although not common. The clay 

 had been deposited in fresh water, and had been laid 

 down most likely in a lake. The Bacillaria in the clay of 

 the trap rocks of New Jersey are thus established. 



The trap rock was of volcanic origin melted into a tar- 

 like substance and ejected upwards through the Newark 

 sandstone. The clay in the faults, the accompanying 

 silica, the chalcedony, smoke quartz and opal point to 

 water, (not very hot) being present. Most likely the 

 crystals or trap were formed in the melted rock which 

 solidified. But it looks as if it was erupted after the New- 

 ark sandstone was formed, in fact after the mud that 

 formed the sandstone began to be made into solid rock. 



