230 ANNUAL OF SCIENTIFIC DISCOVERY. 



ence. Should remains of still older organisms be found in those 

 rocks now known to us only by pebbles in the Lauren tian, these 

 names will at least serve to mark an important stage in geological 

 investigation. Amer. Jour. Science, L. (1870), pp. 130-132. 



LAURENTIAN ROCKS OF EASTERN MASSACHUSETTS. 



The investigations of Hall, Logan, and Cooke, in the Highlands 

 of New York and New Jersey, have left no doubt that the lime- 

 stones which were formerly supposed to be altered Silurian rocks 

 are really of Laurentian age. At the meeting of the American 

 Association for the Advancement of Science, at Salem, in 1869, 

 the view was advanced by Sterry Hunt that the same might be 

 the case with the similar rocks of Eastern Massachusetts. Dr. 

 Hunt showed that this was probable, not only on lithological 

 grounds, but also from the fact that the Laurentian rocks appear 

 to the southward of the great palaeozoic basin in New Brunswick 

 and Newfoundland, which are geologically but a north-eastern 

 prolongation of New England, and, moreover, from the out- 

 cropping of the lowest Silurian strata at Braintree near Boston. 

 Subsequent microscopical examination revealed the presence of 

 the Eozoon Canadense in a serpentinic limestone from Newbury- 

 port, and better specimens were obtained about 28 miles south- 

 west of Newbur} 7 port, in the limestone quarries of Chelmsford. 



The continuous and complete calcareous skeleton of the fossil 

 does not appear in these specimens, which seem, like some por- 

 tions of the rock from Grenville, as described by Sir William E. 

 Logan, to be made up of fragments of the calcareous shells of the 

 Eozoon, mingled with grains of serpentine, and cemented by 

 crystallized carbonate of lime. In the specimens from Grenville, 

 and from most other localities, the mineral matter replacing the 

 sarcode and filling up the canals and tubuli of the calcareous 

 Eozoon skeleton is generally serpentine, or some other silicate. 

 In the Chelmsford specimens, however, the injected mineral is 

 like the shell itself carbonate of lime, though readily distinguish- 

 able from it by difference in texture and transparency. In this 

 connection it should be said that the crystalline rocks of Newbury- 

 port and Salisbury, although separated, in Hitchcock's geological 

 map, from the gneisses to the south-west, and united to the 

 sienites of Gloucester and Rockport, seein very unlike the 

 latter, and closely related lithologically to the gneiss of Chelms- 

 ford, which encloses the crystalline limestone. Amer. Jour. 

 Science, January, 1870, p. 76. 



THE WHITE MOUNTAINS. 



At the Troy meeting of the American Association, Professor 

 C. H. Hitchcock, of the New Hampshire State Geological Survey, 

 exhibited an interesting model of the White Mountains, made 

 from data obtained by a careful examination of the group by 

 himself and his assistants. The model was made of superimposed 



