. The Canadian journal ; a repertory of industry, science, and art ; and a record of the proceedings of the Canadian Institute. 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 sur
. The Canadian journal ; a repertory of industry, science, and art ; and a record of the proceedings of the Canadian Institute. 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 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 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 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
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