John Adie, Esq., on the Marine Telescope. 117 



northern drift of Europe and that of North America ; for fos- 

 sils of that genus are now known to occur upon the northern- 

 most point of the western extremity of North America, in New 

 England, in Northern Europe, as well as all over Siberia. 



To the second period we would refer the stratified deposits 

 resting upon drift, which indicate, that during their deposi- 

 tion the northern continent had again extensively subsided 

 under the surface of the ocean. 



During this period, animals, identical with those which 

 occur in the northern seas, spread widely over parts of the 

 globe which are now again above the level of the ocean. 

 But, as this last elevation seems to have been gradual, and is 

 even still going on in our day, there is no possibility of tracing 

 more precisely, at least for the present, the limit between 

 that epoch and the present state of things. Their continuity 

 seems almost demonstrated by the identity of fossil-shells 

 found in these stratified deposits, with those now living 

 along the present shores of the same continent, and by the 

 fact, that changes in the relative level between sea and main- 

 land are still going on in our day. 



Indications of such relative changes between the level of 

 the waters and the land are also observed about Lake Supe- 

 rior. And here they assume a very peculiar character, as 

 the level of the lake itself, in its relation to its shores, is ex- 

 tensively changed.* 



Description of the Marine Telescope. By JoHN Adie, F.R.S.E., 

 F.R.S.S.A. Communicated by the Author. 



The instrument which has been popularly named the 

 Water, or Marine Telescope, from the power given by its 

 use to see into the water, consists of a tube of metal or wood, 

 of a convenient length, to enable a person looking over the 

 gunnel of a boat to rest the head on the one end, while the 

 other is below the surface of the water ; the upper end is so 

 formed, that the head may rest on it, both eyes seeing freely 

 into the tube. Into the lower end is fixed (water-tight) a 



* An interesting account of the natural terraces around Lake Superior is 

 given at p. 413-il6 of" Lake Superior." 



