QUARRYING. 97 



a "juniper" or with a drill, which is held and turned by one 

 man while two other men strike the head of it. 



The term "jumper" is sometimes applied to long drills, 

 which, when a hole becomes deep, are used as jumpers ; i.e. 

 lifted and struck upon the rock, the weight of the drill and the 

 impetus given to it being, in such cases, as effective as striking 

 the head of it with hammers. 



" Jumpers," properly so called, are usually from 6 to 7 feet 

 in length. They are sharpened at each end, and are swelled 

 out into the form of a thick disc or ball at about half their 

 length, so as to add to their weight, and assist in giving them 

 a rotatory movement. In some quarries, where the rock is very 

 hard, they are not found to answer so well as drills ; but, where 

 applicable, more work can, as a rule, be done with them in 

 a given time than with drills. 



It is usual, in boring rock, to pour water into the hole. This 

 assists the operation by keeping the drill cool, and enabling it to 

 retain its edge better than it would otherwise do. Even the hardest 

 kinds of rock seem to cut better when wet than when dry. The 

 water also forms the dust and small fragments into a paste, in which 

 form they are more easily removed by the " spoon," or scraper. 



If it be required to thoroughly clean out the hole, an extra 

 quantity of water is put into it, which is afterwards removed, 

 in the form of thin mud, by means of a piece of rag (old powder 

 bags), frayed rope, or other suitable material passed through the 

 eyed end of a rod. The holes should always be well dried out 

 before powder is inserted. 



In the quarries at Port Elizabeth (South Africa), from which 

 the stone was procured for the harbour-works there, the rock 

 was quartzite, similar to that at Holyhead. The drilling was 

 performed partly by steam and partly by hand. 



The steam-drills were of the Ingersoll type, and the drills 

 used with them were arranged in sets of six, viz. 3J, 3J, 3, 2f, 

 2J, and 2J inches. They thus diminished at the rate of inch per 

 drill, this being necessary for purposes of clearance. A drill would 

 seldom bore more than 18 to 20 inches without being sharpened.- 



Much time was occupied in moving the machines about the 

 quarry, and placing them in position for drilling, also by stop- 

 pages for repairs. Each machine drilled on an average 84 feet 

 per week. The greatest depth drilled in one day of 10 hours, 

 by one machine, was 26 feet. 



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