520 CJironicles of Science. [July 5 



Geology and Paleontology. — Tlie Geology of the Ottawa Valley 

 has been described in a lecture delivered before the Ottawa Natural 

 History Society, by Jas. A. Grant, M.D., F.B.C.S.E., F.G.S. The 

 whole of the rocks beneath the drift are older than the grey sand- 

 stone of the New York series, which corresponds to the Llandovery 

 beds or Middle Silurian of Britain (see ' Eeport of Geology of Canada, 

 Murchison's' Siluria,' chap, xviii., and ' Lyell's Elements of Geology,' 

 6th edition, p. 566). The lowest formation described (leaving out 

 the metamorphic rocks) is the Potsdam sandstone, equivalent to the 

 Upper Cambrian of Lyell, and to the lowest members of the Lower 

 Silurian of the Geological Survey of Britain. It crosses from 

 New York State into Canada, being well developed in the county of 

 Beauharnois (see ' Lyell's Elements,' p. 577). Above this is the 

 Calciferous Sand-Bock, which, in that part of Canada, is principally a 

 granular magnesian limestone, with some imperfect fossils. Its 

 thickness is about 300 feet. The Chazy limestone, next in the series 

 is, in Canada, associated with sandstones and shale. It forms a zone 

 around the Geological depression between the Ottawa and the St. 

 Lawrence. Above this formation is a great mass of limestones, 

 divided by the New York Geologists into three formations — the 

 Bird's-eye limestone, the Black Biver limestone, and the Trenton 

 limestone. In Canada, however, these divisions are indistinguishable, 

 either lithologically or palaeontologically, consequently they are 

 united, and constitute the Trenton group, which forms, according to 

 Sir W. Logan, one of the most persistent and conspicuously marked 

 members of the Lower Silurian rocks of North America. It is 

 found largely round the city of Ottawa. Its thickness is probably 

 not less than 600 feet ; but dislocations make the amount difficult to 

 estimate. The next formation is the Utica Slate, consisting of dark- 

 brown bituminous shales, interstratified here and there with a few 

 beds of dark limestone. In some places, the shale is sufficiently 

 bituminous to produce mineral oil in considerable quantity. The 

 drift formation extends over North America, north of the parallel 40°, 

 and forms the surface of country over a great part of the triangular 

 area included by the St. Lawrence and Ottawa rivers. It consists of 

 stratified clays and sand, with erratic boulders, many of them of great 

 size. The channel of the Ottawa is contracted in various places by 

 ridges of drift. The post-glacial beds are divided by Dr. Dawson 

 into two series, the lower being the Leda Clay, a deep-sea deposit ; 

 the upper, the Saxicava Sand, formed in shallow waters. Amongst 

 the clay fossils are Saxicava rugosa, Tellina Greenlandica, and the 

 Mallotus villosus or capeling of the lower St. Lawrence. [This is 

 the little fish mentioned by Agassiz as the only tertiary species which 

 he was able to identify with a living form. It is found in nodules 

 of clay in Greenland. (i These nodules exemplify the operation of the 

 dissolving soft parts of the fish in consolidating the surrounding 

 matrix," ' Owen's Palaeontology,' 2nd edition, p. 174.] The same fossil 

 is found in nodules, in clay at Fort Coulogne Lake, at 365 feet above 

 the sea. Most of the boulders are composed of gneiss, either ordinary 

 or hornblendic. [ In connection with this subject, see an interesting 



