Davis — Quarries in the Lava Beds at Meriden. 5 



account of the use of it for a number of years past as one of 

 the stopping places for a week or two of our summer course in 

 geology : thus the ground has been carefully and repeatedly 

 explored by teachers and scholars, and the explanations sug- 

 gested to account for its structure have been subjected to close 

 scrutiny. A brief account may be given of the evidence on 

 which the extrusive origin of the three lava sheets rests. 



In all three sheets, the upper surface is vesicular where 

 exposed near the base of the back slope. This makes a strik- 

 ing contrast with the dense upper surface of the East Rock and 

 West Rock sheets, and at once raises a strong presumption in 

 favor of extrusion. Not satisfied, however, with this alone, 

 careful search has been made for critical contacts and struc- 

 tures in the sheets of the separate blocks. 



In the Higby block, the lower part of the anterior sheet con- 

 sists in part of volcanic ash and lava blocks ; at the upper sur- 

 face of the sheet numerous detached fragments of vesicular 

 trap have been found in the sandstone. The main sheet also 

 is immediately overlain by a sandstone containing many frag- 

 ments of vesicular trap. No evidence for the posterior sheet 

 has been found. 



In Chauncey block, the anterior sheet has a bed of ash and 

 lava blocks at its base; and its upper vesicular surface is 

 covered with sandstone containing many trap fragments, well 

 shown when the reservoir was in process of construction in 

 the anterior valley. A gulley on the back slope of the 

 main sheet discloses an overlying stratum of sandstone hold- 

 ing amygdaloidal trap. A railroad cut at the southern end 

 of the posterior sheet exhibits the usual "mixture" of vesicu- 

 lar trap fragments in the sandstone, as if a clinkery field of 

 " aa "—in the Hawaiian sense — had been buried by a deposit 

 of sand and mud: the fresh-cut rock here exposed several 

 years ago frequently revealed minutely stratified sediments in 

 the open vesicles of the trap, both in the loose fragments and 

 in the back of the sheet itself ; and the stratification of these 

 little deposits was always parallel to that of the adjacent sand- 

 stones and shales. 



In Lamentation block, the base of the anterior sheet con- 

 tains the heavy bed of ash and lava blocks that has in recent 

 years become well known to the people of Meriden, but 

 unfortunately under the name of " the volcano." There is no 

 evidence of any vent or local eruption to be found. The back 

 of this sheet has the usual " mixture," and among the basal 

 beds of the overlying sandstone there is a stratum of tuff-like 

 nature. The back of the main sheet at its northern end is cut 

 by Spruce brook so as to expose the sandstone where it filled 

 the spaces among a confusion of vesicular fragments. The 



