113 



magnesian, being more properly a dolomite than a limestone ; 

 but usually a considerable proportion of the magnesia appears 

 to be in the form, not of a carbonate, but of a silicate — 

 serpentine and bowenite. This is, I believe, the only serpen- 

 tine-bearing rock in the Huronian series of this region. The 

 best known deposits are in Newbury. In early colonial times 

 these were extensively wrought for lime, and "Devil's Den" 

 and ' ' Devil's Basin " are the modern designations for the long- 

 abandoned quarries. There is considerable serpentine at these 

 places, but it is not uniformly distributed through the lime- 

 stone, which also contains asbestus, wollastonite (Mr. Wads- 

 worth has shown that this radiated, fibrous mineral is not 

 tremolite), and siderite ; though, unlike the similar deposits in 

 the Montalban system, it is not rich in accessory minerals as 

 regards either variety or quantity. The question has been 

 raised as to whether the Newbury limestone is endogenous or 

 indigenous. I am well satisfied in my own mind, however, 

 that these deposits are truly stratified. At the Devil's Den, 

 especially, the lines of bedding are very distinct in a portion of 

 the rock, and, moreover, the strike is parallel with the trend 

 of the mass, N.E.-S.W., while the dip is steep to the N.W., 

 agreeing with the stratified diorites on the north and the petro- 

 silex on the south. In fact, the stratification is as well pre- 

 served in all the limestone as could be expected, considering 

 the great disturbance and alteration exhibited by the enclosing 

 diorites. These last, as can be seen on the map, belong to the 

 exotic or "mixed" series; they include much granite, and 

 appear entirely devoid of stratification. The question may be 

 asked how, if the limestone is contemporaneous with the diorite, 

 any of its bedding has survived the disturbance which entirely 

 destroyed that structure in the diorites ? The answer is found 

 in the nature of the rock. Limestone, like quartzite, is an 

 inert substance, little susceptible of metamorphism ; and the 

 ordinary metamorphic agents, — heat and pressure in the pres- 

 ence of water, — while competent to soften and extravasate 



OCCAS. PAPERS B. S. N. H. — III. 8 



