The "Rock-render."

Cromwell Argus, Volume III, Issue 135, 11 June 1872, Page 7

The "Rock-render."

A new product of local industry, styled the " Hock-render," being a new kind of blasting powder, manufactured by Messrs Bolton and Elder, of Port Chalmers, was successfully tried the other day in one of tbc Port Chalmers quarries. A number of gentlemen, including several from Duucdin, were present. The bole pierced in the solid rock was 4ft. i)in. deep, and 2in. in diameter. The " Rock-render" was deposited in the bole to a depth of 11 inches only, and the fuse attached was then tamped down in the ordinary way. The explosion took place within three minutes from the word " lire" being given, and split the rock without ejecting any small pieces. Those present were much pleased with the result of the experiment; in fact, so safe did it appear to be that it was considered anyone might have been within a fcw r feet of the explosion without injury. The " Rock-render" is from 30 to 40 per cent, stronger than blasting powder, and can be sold at 2d. per pound cheaper. It is also safer to handle, as, previous to the experiment described above, a small quantity was ignited but slowly smouldered away without exploding or going off with a puff. It is, indeed, one of the chief recommendations of the " Rock-render" that it will not explode unless confined and well tamped. One of the experienced quarrymen at the work stated that it took lil lbs. of powder to produce a similar effect, whereas in this instance 1 lb. only of the "Rock-render" was used, thus showing a great saving. The manufacturers are to be congratulated on the success of the experiment.— Daily Times.