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Show H - Hardness of Tantalum. H J Tan'ulum has been hammered into H c -ih-rts which are extremely hard,. H Sir William Crookes, F. It. 8., states H ft Lbnt "a bolo had to bo bored through H ,r i pinto of this metal and a diamond H i fer irlll was used, rovolvlng at tho rare H' f f if 5,000 revolutions per minute. This H fe ..lilrllng forco was continue ! r';se- H ft cssly for thrco days and n!ats when H : ,t was found that only a small do- H; V' ' jression 0.25 fnllllmetor deop had HE f ooen drlllc' and It was -i moot oolnt t f jfhlch hr 1 - 'n fl tho moio damage Hj" f th- "a ii r tho tantalum." Sck B . i, -t. ... .monuui. : , |