MERIDEN ASH BED. 67 



ure appears around many of the blocks in the midst of the breccia. These 

 blocks graduate outwardly into glass, and so have been rounded in place 

 by remelting. Where they are large and angular they have been carried 

 but a little way from the base where they were formed ; where they are 

 small and spherical they are far-carried and much resorbed in the glass 

 mass. 



The locality is peculiar for the great quantity of basic pitchstone, 

 which, while greatly mixed with sand and trap fragments for a few feet 

 up, is an almost pure shattered green to liver brown pitchstone (red 

 brown by transmitted light) for 20 feet above. It has the fine conchoidal 

 fracture and the greasy luster of a pitchstone. It is sparingly spherulitic 

 and has at times a fine perlitic structure, and the minute egg-shaped 

 or spherical spherulites slip out of their places with polished surfaces. 

 The lens shows sparingly minute feldspar-rods and larger pyroxenes and 

 olivines. The structure of the whole is disguised by the intermixture 

 of calcite and ankerite. Large areas of pure pitchstone can be found 

 up the south path, and on the bluff over the blasting is a great block of 

 a fine brown hyalopilitic diabase. 



This breccia bed is said by Messrs Davis and Whipple,* who studied 

 the trap sheets carefully with special reference to the question of their 

 intrusive or extrusive origin, to extend but a little distance north and to 

 be continued a mile and a half southeast. 



ERUPTION OF GLASS BRECCIA THROUGH TRAP SHEET. 



Half a mile north of the last outcrop, is an interesting locality, described 

 by Davis and Whipple as — 



" a local trap conglomerate in the same horizon with the anterior sheet. Vesic- 

 ular and water-worn pebbles are here interbedded with sand, as if this point were 

 not far distant from a wave-beaten margin of the anterior lava sheet." t 



The place is on the same trap ridge and may be found by going north 

 from the last locality along the Berlin turnpike to the point where a 

 road comes in from the southwest. Opposite this road a wood road runs 

 east to the ridge, and going a few rods north one comes to a fine point of 

 view of the lake to the west, where beacon fires have been built. Directly 

 beneath in the bluff is a rock shelter, and the southern wall of this is the 

 south wall of the throat to be described. 



The explosive force of the steam at the base of the trap sheet has 

 formed the same brecciated agglomerate as before, but has here forced its 



* The intrusive and extrusive trap sheets of the Connecticut valley. Bull. Mus. Comp. Zool. . 

 Geol. Series, vol. ii, p. ji8. 

 fI*oc. cit., p. 108. 



X— Bull. Geol. Soc. Am., Vol. 8, 1896 



