Transactions . i mnK ~L~ i- o fu^ II MP j-SUTl 101 o 31 simp si UBT101* (IPT oSob iuJl 03+ c iO =1 ?? > pa, »M laiijoBiu ni aloq JMB^i. 1 -I 3 J-51 Bji q ,ul- sm jp aHI!J 1 1 I n ; p aSi T?T 0 >< Lt c3ub fr ? t ! (.una 3^ T PISJ 9 II! P >3 [« 10 -> - II a«tIC ^--~- 5 o .til! dub I«P )SuBtiof—L 1 imp ?3 IB1 ~^> T) 3a nop IB unt 11 3, ?1!!I © s in l-> (» iISi s C U pun ainuOBiu >« dn . hi )• i © fi. ^ 3 i ^1 1 5 s o lli[.n in at, Ldn (u <y 4J, UI 1*3 ? -* p.! 1 5 3 El » *I! tP U »H -n Own St 10 I t1 , 8 3 a £ JB3 kl) Ml o 1 s X :- C O M - i d! X, u> Ij-I - i \Y
Transactions . i mnK ~L~ i- o fu^ II MP j-SUTl 101 o 31 simp si UBT101* (IPT oSob iuJl 03+ c iO =1 ?? > pa, »M laiijoBiu ni aloq JMB^i. 1 -I 3 J-51 Bji q ,ul- sm jp aHI!J 1 1 I n ; p aSi T?T 0 >< Lt c3ub fr ? t ! (.una 3^ T PISJ 9 II! P >3 [« 10 -> - II a«tIC ^--~- 5 o .til! dub I«P )SuBtiof—L 1 imp ?3 IB1 ~^> T) 3a nop IB unt 11 3, ?1!!I © s in l-> (» iISi s C U pun ainuOBiu >« dn . hi )• i © fi. ^ 3 i ^1 1 5 s o lli[.n in at, Ldn (u <y 4J, UI 1*3 ? -* p.! 1 5 3 El » *I! tP U »H -n Own St 10 I t1 , 8 3 a £ JB3 kl) Ml o 1 s X :- C O M - i d! X, u> Ij-I - i \Y< p III = < el O 5 1 paifjom jiua \ 3 i03-1 ima S3 2 S OH JO 2 c 53H ONI K 5 3 e |5 C 5 | e 1 -| | i 1 -Q31 3 llUC g 3S3 5 £ lOH JO I s S3h I i IONa I 1 i 3 ) 1 ; 1 I <f I11 5 C — 170 ROCK-DRILLING ROCK-DRILLING ECONOMICS. 171 In these charts the horizontal lines represent time of performance andthe vertical lines distance drilled. The completeness of the charts will be noted; every minute of the9-hr. working shift is accounted for. For instance, Fig. 13 shows that the actual drilling did not begin The machine then drilled a hole 16 in. deep in 3 min., when itwas stopped to change steels, which operation required 1 min., aDd afurther distance was then drilled of 20 in., requiring 3 min., when themachine was again stopped to change steels, 4 min. being consumed indoing so. Drilling was then continued and the hole deepened 15 in. min. The total time consumed in actual drilling was min.; totaltime changing steels, 5 min.; and total depth of hole, 51 in. At this stagethe machine was shifted for drilling a new hole. In the city of Pittsburgh Jackhamers are being employed for drivingan 8 by 12 ft. sewer tunnel, 1,200 ft. long. The formation is a hard slateand
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
