268 American Association. 



species of Fleuroiomaria, known in America in the Trenton 

 Limestone^the P. subconica (Hall) — comes so very near to one 

 of our fossils, that it miglit well be only a variety of the species. 

 The Highland fossil has rather more numerous whorls, and per- 

 haps a broader band. The genus Oncoceras, so characteristic of the 

 Trenton Limestone, also occurs, but of a larger species, with more 

 numerous septa than the 0. constrictum. As the calcareous 

 beds in Canada frequently contain the fossils of more than one 

 suh-division of the New York series, it is not more than we should 

 expect, to find the above fossils associated in a single thick band 

 of limestone. It is most satisfactory to find, in the northernmost 

 part of Scotland, the representatives of the Calciferous Sandrock 

 and the Trenton Limestones — as in the South of Scotland, that of 

 the Chazy limestone.* And as the former repose upon a quartz 

 rock with abundance of fucoidal impressions, the suggestion is 

 obvious that such rock Hi ay, perhaps, occupy the place of the 

 Potsdam sandstone. 



Note. — Mr. C. Peach is now proceeding, at my special request, 

 to endeavor to collect more fossils, not only at Durness, but throixgh- 

 out the Assynt and other tracts into which the same limestones 



and quartzites extend. 



J. W. Salter. 



DRESSING METALLIC ORES. 



A more practical subject than the majority of those discussed 

 in this Section, was introduced by Prof, Silliman, This new 

 method devised by himself, appears fitted to effect a very import- 

 ant saving in labour, and if so it must greatly facilitate the work- 

 ing of our Canadian mines, in districts where labor is dear and 

 not easily obtained. 



" Professor Silliman gave a brief description of a new 

 system of dressing Metallic Ores. The Professor said the object 

 of his remarks was to describe the general principle of a system 

 of ore dressing, devised and put in practice at the Copper Mines 

 of the Bristol Mining Company at Connecticut, under his own 

 direction. The main features of this system are the perfect sepa- 

 ration of the finer portions of the product of stamping and crushing, 

 commonly known as, "Slime Ore," from the coarser portions, with- 

 out the aid of sieves or screens, — the application of the well known 

 system of jigging directly to the stamped ore, Avhich has hitherto 



* The great Madurea of Grivan, m Ayrshh-e, has been identified with 

 tlie M. magna (Hall) by Prof. McCoy. 



