Geology and Natural History. 305 



cano," he would have found them in the trap region of Connecti- 

 cut. In reply to this we would state that no region of igneous 

 rocks, volcanic or otherwise, was ever studied with more care or 

 with a more exact determination of the facts, than that of Con- 

 necticut by Percival. We have followed him over and among the 

 various trap ridges of the Connecticut valley, and know positively 

 tluU the trap eruptions were in all cases, eruptions through fissures, 

 as Percival states, and not by volcanoes. We deprecate this 

 throwuig doubt over the accurate observations of others, by one 

 who acknowledges tliat he knows nothing about the facts. 



'Hiore are l}eds of scoriform rock in the Connecticut valley 

 amo'.ig the stratified beds in the vicinity of the trap. They occur 

 near New Haven, A remarkable locality exists in Durham, on 

 the Air-luie railroad, under a bridge just east of Reed's Gap 

 (a o:ap in the trap hills). At this place, the layer seems to be 

 made up of large masses of scoria, some of them from four to six 

 niches in diameter. But on a careful examination by the writer, the 

 rock proved to be nothing but a scoriform sandstone, particles of 

 quartz, feldspar and othe^r ingredients of the :Mesozoic sandstone 

 being visible throughout the scoria masses, and manifestlv eon- 

 stitutuig them. It is obviously a bed, like others at New fraven, 

 Ihnaigh^ which steam penetrated freely during the trap eruption. 



->Ii'. Brigham also suggests that the formation of trap dikes 

 may now be going on, from time to time, at various depths below 

 the surface; and ""that the high temperature thev bring in con- 

 tact with the cold rock, through which they break,' or info whose 



earthquakes." But there is not an observed fact that authorizes 

 ^s to believe that any eruption of trap has taken place in New 

 iingland since the Mesozoic era. Moreover, earthquakes are not 

 produced by the escape of igneous rock. An earthquake is the jai- 

 from sudden fracture or displacement; it matters nothincr whether 

 I?"^«^*^ ejections follow or not. The breaking of the rock begins 

 the tremor" if not already initiated. The earthquakes of Xew 

 ^^iigland may have resulted from a slight yielding to tension 

 "the rocks somewhere beneath the region shaken, a tension that 

 may i)e a consequence of former upheavals or subsidences of the 

 region, or of unappreciated movements that are now in progress ; 

 1'!" Pt>ssibly of contraction or expansion below due to subterranean 

 ^bange of temperature ; and some of the more local may come from 

 exit *^ gravity in rocks beneath, if openings or cavities there 



6. I'^eUndnary notice of a new species of Trimereila, from 

 tiTV ^7 ^' ^- ^^J^EK. (Communicated by the author).— Among 

 ^^e fossils obtained by the Geological Survey of Ohio (now in 

 hr^l^f '''''^'''' *^® direction of Prof Newberry), and handed me 

 r study, there are from the Niagara group some large casts of a 

 ^^^'-ella, which I had thought might be a variety of T. graudh 

 On comparing them recently with Mr. Billings's typical 

 of that species, I have found them quite different and 



nrnnnrtSonnllv much broader shelk, 



ved beyond 





