162 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
in southeastern and eastt^rii New York State. Not only this, 
but such phenomena as the sedimentary succession on Anticosti, 
and at Perc6, the nature of the early Silurian sediments in New 
York and New Jersey, and the coincidence of slaty cleavage in 
Ordovician and Devonian rocks along the Chaudiere, are pre- 
simiptive evidence of conformable, or nearly so, succession of 
Silurian or Devonian and Ordovician rocks. Devonian and later 
orogenic movements, differential erosion of hard and soft beds, 
and a thick mantle of glacial drift make the task of locating con- 
tacts one of extreme difficulty. 
Constructive suggestions that have the support of field evi- 
dence are difficult to make. I have already made a suggestion to 
explain the difference in attitude between the so-called Cambro- 
Silurian black shales and the Silurian or Devonian sandstone and 
limestone (see p. 149 above). Ells has pointed out that the De- 
vonian rocks of Beauce County, Quebec, along the Chaudiere, 
have suffered just as much metamorphism as the underlying 
"Cambro-Silurian" rocks. He writes: "Siluro-Devonian rocks 
occupy a basin-shaped area of no great extent — but in cleavage, 
conforming to the underlying Cambro-Silurian and Cambrian 
rocks . . . and show clearly that all have been involved in the 
general scheme of folding."^ 
Blackwelder (see p. 137 above) described the belt of deforma- 
tion in the Taconic Revolution as "wide enough to include most 
of New- Bnmswick, perhaps Nova Scotia, nearly all of Maine, 
and probably even Rhode Island" (p. 640). Of the Bruns- 
wickian orogeny (late middle Devonian) he writes: "The tract 
within which the rocks were crumpled during the epoch stretches 
from western Newfoundland through Cape Breton Island, Nova 
Scotia, New Brunswick, Maine, and probably southern New 
England, and was wide enough to include on the northwest the 
Gaspe Peninsula in eastern Quebec" (p. 641). So that, with the 
exception of the New York localities, all of the area supposedly 
affected by the Taconic Revolution is within that affected by the 
later Devonian disturbance, and if necessary, the crumpling 
of rocks of unknown age might be assigned to this latter dis- 
turbance. Moreover, in a few localities the folding once re- 
»EUs, R. W. Trans. Roy. Soc. Canada 1891 , vol. 9, sect. 4, p. 122, 1892. 
