Dale.] 198 [January 3 



Fissures: The strata are fissured at right angles to the axes of 

 these folds which may indicate another system of depressions 

 and elevations with axes running W.NW.-E.SE., 1 but operating 

 in a less powerful manner, as would be the case if the strata had 

 been previously corrugated in an opposite direction. 



The cleavage of the pebbles of the conglomerate is partly due 

 to the fact that the adhesion of the cement was equal to the cohe- 

 sion of the pebbles at the time of the Assuring. A Silurian con- 

 glomerate even occurs in France in which the siliceous pebbles 

 weather more easily than the cement which binds them together. 2 

 Prof. Wolcott Gibbs has suggested to the writer two possible 

 explanations of these fissures. Z, Wave theory : the conglomerate 

 having been acted upon by a wave motion resulting in a succession 

 of vertical breaks at pretty regular intervals. II, Contraction 

 theory : the conglomerate having been heated, as seems probable, 

 and beginning to cool at the extremities of the deposit, the resulting 

 contraction would produce a series of fissures and leave the spaces 

 which were subsequently filled with silica. 



Historical : Mr. W. O. Crosby, after studying the band of 

 hornb]endic gneiss which runs from Concord S.W. to West- 

 borough, Mass., 3 and visiting the hornblendic and chloritic rocks 

 of Smithfield, R. I., 4 and also examining the granite in the towns 

 of Rhode Island to the S.W. of Fall River, 5 at first hesitates 

 whether to call them Huronian or Montalban, but finally assigns 

 them to the Montalban series. If the lithological and chemical 

 tests which underlie Professor Hunt's system may be relied 

 upon for this district that classification is probably correct ; cer- 

 tainly thus far no paleontological evidences have been found in 

 the hornblendic, chloritic, serpentine and mica slates, Kos. 1, 2 

 and 3, to bring any of them into the Paleozoic. On the other 

 hand in view of the highly metamorphic character of many of the 

 overlying rocks it is quite possible that some of these lower rocks 

 belong to the Paleozoic Time. The first member of the section 



1 President Hitchcock finds a double system of elevation. See Geol. of Mass. p. 540. 



2 Oehlert. Silurien de la Mayenne. Bull. Soc. Genl. de France, in Ser., Vol. x, 1882, 

 p. 349. 



3 Geol of Eastern Mass., p. 107, 108. 



4 Ibid., p. 133, 134. 



5 Ibid., p. 127. 



