10 Davis — Quarries in the Lava Beds at Meriden. 



The upper bed, as far as exposed in the quarries, is unlike 

 the lower in many respects. The color of its deeper joint 

 planes, where not affected by weathering, is dark steel-gray, 

 greenish or bluish ; the fresh broken rock is dark gray or 

 greenish, without any of the bright reds or purples of the lower 

 flow. The texture is dense throughout, vesicles and cavities 

 being very unusual : but by following the quarry ridge to the 

 northeast about a third of a mile, one may find the ordinary 

 vesicular structure of the upper part of the bed there exposed 

 on its back slope. The density of the upper bed in the quarry 

 is particularly noticeable where it rests directly upon the roll- 

 ing surface of the strongly colored and highly vesicular lower 

 bed. At the point in the old quarry where the surface of the 

 lower bed is best exposed, the dense, dark lava of the upper 

 bed fits closely into all the inequalities, the two beds being 

 sometimes so closely welded together that weathering has not 

 loosened them along the surface of contact, and hand speci- 

 mens can be broken off showing the two kinds of lava : but as 

 a general rule a weathered seam or parting follows the contact. 

 The columnar jointing of the upper bed is fairly well devel- 

 oped at many parts of the quarries, but it nowhere produces 

 columns of notable regularity. Near the base of the upper 

 bed, the rough joint columns are of small dimensions : half a 

 foot to a foot in diameter. Some fifteen or twenty feet above 

 the base the columns are often two, three or four feet in diam- 

 eter. The weathered joints in the rocks near the surface of 

 the ridge are yellowish in the upper bed, but brownish in the 

 under bed. The former is hard enough for use as road metal 

 to the very top of the quarry, but the latter is weak and rotten 

 where it has been weathered. The stripping of the ridge in 

 preparation for further quarrying exposes many well-glaciated 

 rock surfaces. 



The various original features of the two masses thus 

 described accord so perfectly with what occurs in modern vol- 

 canic districts, and the secondary features result so naturally 

 from the long lapse of time that the rocks have existed, that 

 "a double-bedded lava-flow" seems to be a well warranted 

 name for the whole structure. The most significant features 

 of the structure appear over so large a quarry face, and main- 

 tain throughout so constant a relation that no reasonable doubt 

 can remain as to their meaning. In order to enforce the gen- 

 eral recognition of a conclusion so well supported, I have 

 replaced the ordinary term " trap sheets " with "the more sug- 

 gestive term u lava beds," in the title of this article, and hope 

 that the latter term may come into common use. 



The absence of stratified deposits between the two lava beds 

 may be variously explained. The first bed may have filled the 



