388 ANNUAL OF SCIENTIFIC DISCOVERY. 



For popular experimental lectures on astronomy, chemistry, optics, 

 mechanics, &c., there are two spacious theatres and a laboratory. The 

 steam-engine, the telegraph, the lathe, and the loom, will be exhibited 

 in all their various modifications, and an electrical machine is being 

 constructed of proportions far exceeding anything of the kind ever 

 known or contemplated before. The glass plate already in the build- 

 ing, is ten feet in diameter ! The machine will be worked by a steam- 



engine. 



The front attic of the Panopticon building is occupied by a beauti- 

 fully constructed suite of photographic rooms, and classes have been 

 formed for instruction and practice in the art. Classes are also form- 

 ing in the chemical department, for quantitative and qualitative analy- 

 ses, and for assays of ores." 



ON THE CHARACTER OF THE FOSSILS OF THE POTSDAM SAND- 

 STONE. 



Most of our readers are aware that the Potsdam sandstone lies at 

 the base of the fossiliferous rocks ; being the oldest rock in which 

 organic remains have yet been found. In America almost its only fos- 

 sils are Graplolites, and a small Lingula. (Dr. D. Owen informs us 

 that it is more fossiliferous in the Far West.) In Russia, where it is 

 readily recognized, it holds the same place in the geological scale as in 

 this country, and its characteristic fossils are a Lingula and an Obolus. 



Such being the antiquity of this rock, it is not surprising that the 

 discovery made by Mr. Logan, some two years since, in Canada, of 

 several series of impressions in the Potsdam sandstone, evidently the 

 tracks or traces of some animal of a higher organization than a mol- 

 lusk, should have excited great interest in the minds of geologists. 



These tracks were at that time, carefully examined by Prof. Owen, 

 and pronounced to be reptilian and clielonean, i. e. made by tortoises. 

 To this decision Agassiz did not subscribe ; for, although he had not 

 had the opportunity for the careful and determinative study of the 

 impressions enjoyed by Owen, he said he could not attribute them to 

 tortoises, and thought Owen would regret making such an assertion. 



The result has been in favor of the opinion expressed by Prof. 

 Agassiz, for in the Journal of the Geological Society for August, Prof. 

 Owen, without making the slightest allusion to his former expressed 

 opinion, announces to the world that the impressions are Crustacean. 



