wyn — Track* in racki oftht Animihu group. 145 



with an air-tension of r>M ^m m ); > >s iuiu \ the time required for the 

 bulb to be heated from 25° to 50° was 322 seconds; but wheu 

 the tension was reduced to 2M (•00152 mm ), the time was 4 1 ii 

 »nds. With a perfect vacuum tin 1 time, of course, would 

 have been still much greater. The diameter of the hull, is n<>t 

 given, hut by the formula of ^ 5, paper A, with a very Bmall 

 bulb, the effect of conduction would have been much greater. 



Art. XXI. — Tracks of or</<nti<- origin in rock* of the Ant- 

 mil'ie group ; by A. R. C. Selwyn, Director of the Geo- 

 logical and Natural History Survey of Canada (letter to the 

 Editors, dated Jan. 7. 1890). 



The discovery of even traces of fossils, or what are supposed 

 to be such, in the Animikie rocks of Lake Superior, is an 

 interesting and important fact which I wish to announce 

 through the medium of this Journal. The specimens were 

 collected by Mr. E. D. Ingall of this Survey, and were sub- 

 mitted to Mr. Matthew of St. John, N". B., for examination 

 and comparison. Mr. Matthew has furnished me with the ac- 

 companying very interesting statement of his views respecting 

 them. I have long held the view that the black Animikie 

 shales represented the Lower Cambrian of the Atlantic border, 

 and I have little doubt that sooner or later the Paradoxides 

 and Olenellus fauna will be found in them. They are quite 

 distinct from and unconformable on the Huronian. 



Dear Sir : I have examined the pieces of flagstone and 

 shale of the Animikie group, bearing impressions of various 

 kinds, which you were kind enough to send me for comparison 

 with markings on the flags and shales of the St. John group 

 and other Cambrian rocks. 



These have greatly interested me, and while some are too 

 indefinite to be of value for such comparison, others are un- 

 doubtedly of similar origin with characteristic tracks of the 

 Cambrian rocks here. 



I should observe, however, that the vertical range of these 

 peculiar tracks of the oldest Pakeozoic rocks is not known, and 

 I can only speak of the Animikie forms in comparison with 

 such markings as they appear in the Cambrian sediment of this 

 region. 



I would refer especially to two types of tracks which are 

 present on the pieces sent for examination. One of these re- 

 calls objects which have been referred to Eophyton^ but incor- 

 rectly, as there are two resembling types of tracks in the 

 Lower Cambrian rocks which have been classed under Eophy- 

 ton, of which one only is the true Eophyton of Torell. 



