430 MESOZOIC TIME — REPTILIAN AGE. 



in. Disturbances — Igneous action — Trap rocks. 



Trap ridges and dikes accompany this formation on the Atlantic 

 border. The rocks constituting them are of igneous origin, and 

 were ejected in a melted state through fissures in the earth's crust. 

 It is remarkable that these fractures should have taken place in 

 great numbers just where the Triassic beds exist, and only spar- 

 ingly east or west of them. The igneous and aqueous rocks are so 

 associated that they necessarily come into the same history. 



The era of these ejections is supposed to have begun near the 

 middle of the Sandstone period. But it may have continued into, 

 or been mostly confined to, the period next following the deposi- 

 tion of the beds. Professor Hitchcock reports that near Mount 

 Tom tufaceous layers made of fragments of scoria intervene be- 

 tween the sandstone beds near the middle of the series, proving 

 that the ejection took place before the following beds had been 

 deposited ; but after an examination of the region the author re- 

 gards it as more probable that the appearance of scoria is owing 

 to an escape of steam laterally from between the opened strata 

 during the ejection of the trap of the adjoining mountain. Mount 

 Tom and Mount Holyoke, of Massachusetts, are examples of these 

 trap ridges ; also East and West Eock, near New Haven, and the 

 Hanging Hills, near Meriden, in Connecticut ; the Palisades along 

 the Hudson, in New York ; Bergen Hill and other elevations in 

 New Jersey. 



In Nova Scotia there is a long range of trap skirting the whole 

 red sandstone region and facing directly the Bay of Fundy ; Cape 

 Blomidon, noted for its zeolitic minerals, lies at its northern ex- 

 tremity, on the Bay of Mines. 



In Connecticut the ridges and dikes are exceedingly numerous, 

 showing a vast extent of igneous action. 



The following map (fig. 651), from a more complete one of the 

 State by Percival, will give some idea of their number and posi- 

 tion. They commence near Long Island Sound, at New Haven, 

 just south of the southern portion of the map, where they form 

 some bold eminences, and extend through the State, and still far- 

 ther north, nearly to the north boundary of the State of Massachu- 

 setts. Mounts Holyoke and Tom are in the system. The general 

 course is parallel with that of the Green Mountains. 



Although the greater part of the dikes are confined to the sand- 

 stone regions, there are some lines outside, intersecting the crys- 

 talline rocks and following the same direction. These also may be 

 parts of the system, for .those in the sandstone actually intersect 



