S8 



CANADA AT THE GBEAT EXHIBITION. 



consequence of the rubbing action being confined to the revolving 

 of the friction rollere upon their axles, instead of the inclined 

 plane rubbing upon the pins, or the thread of an endless screw 

 rubbing upon the teeth of a worm->^'heel, which has ouly contact 

 at a little more than a line. This has a scraping action, tending 



[1852. 



constantly to remove the oil from the surface, but in the friction 

 rollers there is a much larger surface in contact to bear the pres- 

 sure, and this surface being always in contact never has the oil 

 scraped off the surface, and can retain the oil for a much longer 

 time. — Civil Engineer and Architects Journal. 



Canada at the Great Exhibition. 



CANADIAN TIMBER TROPHY. 



( Extract from the Official Reports 2nihUshed ly the Iviperial Conuiiissioners of the Great Exhilition q/"1851.) 



Of all the British Colonies, Canada is that whose exhibition 

 is tlie most interesting and the most complete, and one may even 

 say that it is superior, so far a.s the mineral kini^'dora is concerned, 

 to all countries that have forwarded Iheir jn'uduets to the Exhi- 

 bition. This arises from the fact tliat tlic collection has been 

 made in a systematic mannei-, and it results that the study of it 

 furnishes the means of appreciating at once the geological struc- 

 tui'e and the mineral resources of Canada. It is to Mr. W. E. 

 Logan, one of the members of the Jury, who fills the office of 

 Geological Surveyor of Canada, that we are indebted for this 

 collection ; and its value arises from the fact, that he has selected 

 on the spot most of the specimens that ha\e been sent to the 

 Exhibition, and ha.s arranged them since their arrival in London. 



The arrangement that he has adiipted, which is entirely technical, 

 includes eight divisions, \'iz: — Metalliferous minerals, and metals 

 obtained from them; Minerals which require conqilicated opera- 

 tions to render them tit f)r use; Lithographic limestones and 

 minerals employed in jewelery, and in tlie mannfactui-e of glass 

 of various kinds; Various kinds of clays and refractory sand- 

 stones; Rocks furnishing whetstones, hones, and polishing stones; 

 Roeks ami minerals in use for improving soils; Materials used 

 in constinetiou, and rocks serving for architectural decoration; 

 Condinstihlc^ minerals. All these classes include materials, of 

 great interest, for industrial pur]iose.s, and we think it useful to 

 mention some more s]iecially. The ores of iron require notice 

 first of all for their abunlanco and excellent quality, as the mag- 



