ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 735 



The lesson to be learned from these microphotographs is that 

 having proper views of transverse and radial lengthwise sections, and 

 of sections perpendicular to a radius, of a standard piece of timber 

 resisting certain standard or minimum strains, all timber having 

 fewer rings per inch of tree diameter, fewer fibres, and fewer and 

 shorter radial plates per square inch of section, should be rejected as 

 not up to the standard, and applied for other purposes or used with 

 a greater factor of safety. 



This method has the advantage of enabling every stick of timber 

 in a bridge to be inspected and judged, and is offered as an interesting 

 and valuable aid to the breaking tests made by the machine. 



In this connection I may offer as the parallel in metal-work two 

 portions of pure Lake copper, one an ingot as ordinarily found, in 

 which the grain is coarse and crystalline, the colour dark red, and 

 the mass full of blow-holes ; this is an average sample of copper 

 casting. The other is run from the same pig, at the same heat, and 

 in a similar mould, but with proper precautions to prevent oxidiza- 

 tion ; in consequence, there are no blow-holes, the grain is close and 

 fine like that of the best bronzes, and the colour is salmon, which is 

 the true copper colour. The " deoxidized " casting weighs 25 per 

 cent, more than the ordinary casting from the same pattern, 

 calipering the same. For these I am indebted to the Philadelphia 

 Smelting Works, Twelfth and Noble Streets. 



Tests made of the deoxidized copper rolled into sheets '035 

 inch thick showed on strips 2 inches wide a tensile strain of 33,760 

 lbs. per square inch, ordinary fine copper in sheets being quoted 

 by Trautwine at 30,000 lbs. This would show 12*5 per cent, 

 superiority in the metal Laving the fine fracture. No. 20 " deoxidized " 

 wire shows a calculated tensile strength of 45,000 lbs. per square 

 inch, and still later tests of wire of the same thickness showed a 

 calculated tensile strain of 41,056 lbs. per square inch for the 

 ordinary, and 47,552 lbs. for the deoxidized, a striking confirma- 

 tion of the indications of the Microscope." 



The Microscope in Metallurgy. — A paper on this subject by M. 

 Atwood was recently read before the San Francisco Microscopical 

 Society. 



In a former paper on " The Microscope in Geology," the author 

 remarked that the Microscope in mining would soon become as impor- 

 tant an instrument in guiding the miner in his operations as the com- 

 pass was to the navigator, as only by the aid of the Microscope could 

 be correctly determined what was so necessary for him to know, 

 namely, the true character of the inclosing rocks of the different 

 metalliferous veins he was either prospecting or working, and thereby 

 rendering mining a less hazardous undertaking, and not allow the art 

 to degenerate into a mere " trial-all " system. We are now only 

 beginning, in the author's view, to understand and realize the great 

 value of the Microscope in metallurgy. One of its most important 

 uses, however, and to which he more especially calls attention, is in 

 the milling of gold quartz, where it has aided in distinguishing and 

 proving in the most unmistakable manner the true condition of the 



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