Inventors at work, with chapters on discovery (1906)
Iles, George, 1852-1942 · New York, Doubleday, Page & company · leaf 129
92 FORM—DRILLS fields, or to the geologist who reads at a glance the compositionof a mineral, the forces which have impressed it age after age.Such drills, set with bortz diamonds, have accomplished remark- … A common drill removes awhole circle of stone. A ring drill removes much lessstone with the same effect. able feats. In boring out 260 columns surrounding the dome ofthe capital at Springfield, Illinois, cores 22^ inches in diameterwere removed from holes 24 inches wide; without sacrifice…
Inventions · Inventors
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