File:Machinery and processes of the industrial arts, and apparatus of the exact sciences (1869) (14597253800).jpg

Identifier: machineryprocess00barn (find matches)
Title: Machinery and processes of the industrial arts, and apparatus of the exact sciences
Year: 1869 (1860s)
Authors: Barnard, Frederick A. P. (Frederick Augustus Porter), 1809-1889
Subjects: Machinery Scientific apparatus and instruments
Publisher: Washington, Govt. print. off.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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iron ring fitted to the extremity of a steel tube fromwhich it may be removed at pleasure, and carrying eight black diamondsfirmly set in its circumference. These eight diamonds are set alternatelyon the inner and outer edges of the face of the ring which is presentedto the rock. The mineral called here black diamond, is essentially thesame thing as the transparent gem of the same name, but is of greatlyinferior value. It is found both crystallized and uncrystallized j but, forthe purpose required in this operation, the uncrystallized form is pre-ferred, as presenting no natural cleavages. The mineral is sold byweight, its cost being proportioned to the weight simply, and not to the 104 PARIS UNIVERSAL EXPOSITION. square of the weight, as is the case with the precious diamonds. Thecost of a ring, such as is described above, is 175 francs, or $35. The diamond perforator penetrates the rock, of course, by friction andnot by percussion. It receives, therefore, from the motor a motion of
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LJ Perrets Water-engine. ferrets water-engine coque s engine. 105 rotation, being pressed in the meantime firmly against the rock byhydraulic pressure applied through a second independent cylinder andpiston. The experiments which have been made with this perforatorgive results which promise important economical advantages from itsuse in rock-boring. Some of these results are as follows: Under a pressure of eight atmospheres, 100 turns of the perforator perminute give: in old mica schist, containing little quartz, 1.2 inch; insimilar rock, with much quartz, 0.4 inch to 0.6 inch; in quartz from thetunnel of Mont Cenis, 0.56 inch; in very hard dolomitic limestone 0.8inch. Under the same pressure, increasing the number of turns of the perfo-rator from 100 to 250 per minute, the advance is very exactly twice anda half as great as before, showing that the effect is proportional to thevelocity. In order to produce a velocity of 100 rotations per minute, an expen-diture of seventy-five litres

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