THEOBY. 445 



cations we should suppose that we were rising higher and higher in the Silurian series. 

 There may be a repetition of rocks often, as is probably the case in the Stockbridge limestone 

 at Middlebury and Cornwall. It should be observed, also, that the force which breaks the 

 continuity of the strata exerts its maximum power nearest the Green Mountain range 

 and hence may be regarded as proceeding outward from it ; and hence, too, the frequency 

 of fractures is proportioned to the nearness of the strata to the disturbing range. Thus, 

 near Williamstown there are five well-defined fractures within a distance of two miles. 



Three difficulties are experienced in tracing out the connections of the Taconic rocks. 

 1. The numerous disturbances of the strata. 2. Vast amount of denudation, which has 

 crowded rocks unequally, owing to their different capacity for resisting decomposition. 

 3. Obscuration of lines of union between different rocks by alluvium. The most difficult 

 point to find distinctly exhibited, is the dislocation between the Taconic slates and the 

 Hudson River slates. As the rocks are similar, and much crushed at the line of contact 

 so that all fossils are obliterated, it is very difficult to draw the exact line of demarcation. 

 In general the Taconic slates have been elevated higher than the Hudson River group. 

 Hence this elevation, and all other disturbances, must have been subsequent to the depo- 

 sition of the Hudson River group. 



Dikes. It is remarkable, in a region so thickly strewed with faults, that dikes are 

 not more common. We see them in Vermont in the marble upon Mt. Eolus, Danby 

 Mountain, in the limestone at North Dorset, in marble quarries in the southwest part of 

 Rutland, and a number in Chittenden County. Dikes are not as numerous in general in 

 the Taconic as the Silurian rocks, except upon Pottier's Point, in Shelburne. It is not 

 absolutely certain, however, that these slates are Taconic. 



Organic Remains of the Taconic System. 



Every member of the system is fossiliferous in Vermont, though the remains are often 

 scanty. The granular quartz holds the oldest animals in North America, and probably 

 the oldest relics of life, even older than the Oldhamia antiqua of Murchison. As the base 

 of the Palaeozoic rocks, it is interesting, because we can obtain some glimpse of the rudi- 

 mentary condition of the earth at this partially finished stage of its history. The condi- 

 tions under which the granular quartz was formed must have been peculiar a condition 

 of higher temperature, and greater energy in the action of chemical forces. 



The most striking points in the life of the Taconic period are : 1. The simplicity of the 

 organization of the animals ; and 2. The very small number of individuals that existed. 

 The animals belong to the Radiata, Mollusca, and Articulata, and are represented by 

 some of the lowest types in all these sub-kingdoms. The Articulata appear only in the up- 

 permost members. If animals had been abundant in the Taconic ocean there is no reason, 

 from the metamorphic character of the rocks. at least the most important of them why 

 they should not have been preserved. Hence there is a general conformity between the 

 life of the Taconic system, in America, and the Cambrian, in Europe. 



The fossils of the granular quartz in Vermont, are obscure fucoids, Scolithus linearis, 

 crinoidal columns, a Linyula, a mollusk resembling Modiolopsis, and a small Orthoccratite. 

 Out of Vermont only the Scolithus and two species of sponge have been found the 

 Palceotrochis major and P. minor. 



In the Stockbridge limestone in Vermont, several genera of corals occur, viz., Stictopora, 



