T.S. Hunt on the Crystalline Limestones of N. America. 199 
masses, is analogous to the interrupted stratification and lenticular 
beds, frequently met with in fossiliferous limestones. 
The limestones of Bolton, Chelmsford and the adjoining towns, 
the v 
riety of fine crystallized minerals which they contain. Among 
these are apatite, serpentine, amianthus, tale, scapolite, pyroxene, 
petalite, chondrodite, spinel, ciunamon-stone, sphene and allanite, 
which include the species characterizing the Laurentian and 
Lower Siturian metamorphic limestones. The limestone of these 
quarries evolves a very fetid odor when bruised. Chromic iron 
ore has never, so far as I am aware, been observed with the ser- 
pentines of this region. 
e have now to inquire as to the geological age of this great 
mass of crystalline rocks which is so conspicuous in Eastern New 
England. Mr. Logan has shown that the rocks of the Devonian 
System in Gaspé, assuming the Oriskany sandstone as its base, 
attain a thickness of more than 7000 feet, and as they are still 
mediate gneissoid, and hornblendic rocks, with their accompany- 
ing limestones, are the Devonian strata in an altered condition. 
of. Agassiz, from his own examivation of the region, was led 
'o a similar conclusion as to the age of the so-called syenites, and 
in August, 1850, presented to the American Association for the 
Vanieement of Science at New Haven, a paper on the Age of 
, Metamorphic rocks of Eastern Massachusetts, which has never 
I believe been published. ‘The less altered limestones which, 
aeording to Dr. Hitchcock are found interstratified with red 
slates at Attleborough and Walpole, may correspond to those 
Which with similar slates and sandstone, are met with at the base 
of the carboniferous formation in Canada on the Bay de Chaleurs, 
in New Brunswick. 
