66 B. K. EMERSOxNT — DIABASE PITCHSTONE AND MUD ENCLOSURES. 



The rounded bomb-like masses of the compact and crystalline trap 

 which are contained in this breccia graduate superficially through hya- 

 lopilitic trap into the green glass, and while compact at center are toward 

 the surface full of radiating steam pores. They seem to have been often 

 carried aloft by the explosions into the still liquid glass, partially melted, 

 and made superficially plastic by reheating, so that the steam has been 

 able to struggle to the surface from the outer portion. 



Among these blocks are many long sheets and rounded masses con- 

 nected by narrow necks, which could not have been blown into the air 

 and have fallen as common bombs (see plates 5 and 6). 



A little way north of the quarry one can climb up the whole face of the 

 trap by a steep path, and 60 feet from the base can study the top of the 

 breccia. Here are unusually large masses of sand frothed up into an 

 amygdaloid sandstone and filled with water-deposited silicates (see plate 

 7, figure 3), and above this the trap is normal and crystalline and full of 

 steam holes for a few feet, and then graduates into the common columnar 

 trap of the upper part of the sheet.* 



MERIDEN "ASH BED:' 



The bed at the base of the trap sheet west of Lamentation mountain, 

 on the Berlin turnpike, two miles north of Meriden, has excited much 

 interest locally, and some blasting has been done by the Meriden Scien- 

 tific Society to open it for study. It differs from the Greenfield bed only 

 in the much greater quantity of glass and in being only half as thick. 

 The glass breccia rests in places upon unbaked sandstone, which is thrust 

 up into it in sheets and tongues several feet, and there changed into an 

 exceedingly tough quartzite by being soaked full of the glass (see plate 9, 

 figure 1). Just south of the blasting the basal bed of compact trap can be 

 followed for three rods to where it is covered, and the glass above sends 

 tongues down into it, showing that they are continuous and in place. 

 Above this basal sheet the trap blocks in the breccia are rare, small, and 

 confined to the top of the sheet. At the blasting the basal bed has been 

 carried up into the glass above by explosions, sometimes as broad sheets, 

 sometimes as rounded and remelted blocks, with peripheral steam holes, 

 and the breccia rests on the sandstone. One such rounded and bomb- 

 like mass rests here directly on the sandstone, and the sand and glass 

 mixture wraps around it, producing exactly the effect of a bomb fallen 

 on yielding sand ; but this sand and glass mixture wraps clear round 

 the block and nearly or quite meet above it, and the same fluidal struct- 



* In reporting my brief accovint of this case, also, Professor Dana has destroyed the meaning of 

 the whole by an error. He says that the trap sheet rests on coarse sandstone breccia 12 to 16 feet 

 thick, instead of coarse trap breccia. (Manual of Geology, 1895, foot-note on page 805). 



