LITHOFRACTEUR.

Tuapeka Times, Volume VII, Issue 335, 4 March 1874, Page 3

LITHOFRACTEUR.

An article in the " Times " of 25th October on the new harbour works at Jersey contains the following description of the operation of lithofracteur as an explosive agent : —

The material to be excavated is a very bard and dense syenite, traversed by broad bandß of trap rook, whLh puts the metal of the boring, tools and tbe patience of the workmen alike to tbe test. Blasting is, of course, largely resorted to, and for some time past tbo engineer of tbe works has been endeavoring to find an explosive compound which would successfully supersede gunpowder. To do this it was requisite that it should be more powerful and no less safe than tbat material, and above all, it was necessary that it should be capable of withstanding the action of water for a time. The reason for this is tbat there are circumstances in which the explosive can be placed in clefts of tbe rocks at low water and allowed to remain there until tbe tide has risen over it, when it can be fired with good effect, the water offering great resistance to the action "of the explosive. The nitro-glycerine compounds offering tbe desired facilities, Sir John Coode selected tbe litbofracteur of Messrs. Krebs and Co., of Cologne, for trial, and some practical experiments witb tbat material have recently been made on the new harbour works by Herr Engels and Mr. Perry F. Nursey. Tbe operations consisted firstly, in the removal piecemeal of a large mass of rock standing out to sea in front of tbe Hermitage Rock, and wbicb bad been partially removed by powder blasting. Small charges of lithofracteur were distributed over tbe rock in boreholes and crevices, and fired simultaneously, bringing down large masses of tbe refractory material, and otherwise so loosening tbe main bulk as to render it an easy prey to the quarryuion, who followed up each blast with a vigorous application of crowbars and hammers. On one occasion when the explosive experiments were being conducted, the new Governor of Jersey, General Norcutt, Avho bad only arrived in tbe island a few days previously, visited tbe barbour works with his suite.' After being conducted over tbe works by Sir John Coodc and Mr. Imrie Bell, the resident engineer, the Governor desired to see some experiments made with lithofraoteur, to, demonstrate its safety and its power, as well as its strength, as compared witb gunpowder. Mr. Nursey, therefore, lighted a cartridge witb a f uzee, which simply burned slowly away ; he then inserted a capped fuze into a similar cartridge, lighted the fuze, and threw the cartridge into a pool of water, when it exploded with a violent report. Two sfeofc lengths of 60-lb contractor's rail of tbe Sandberg section were than placed on tbeir sides on sleepers with a 4-feet bearing. On the web of one was laid a bag containing half a pound of blasting powder, and on tbat of tbe other a similar quantity of litbofracteur loosely tied up in paper, eu.pi» p»oUot bom 6 inxaA £o* firing: The fuzes were lighted, and in a few minutes tbe powder went off like a puff of steam ; a few minutes later the lithofracteur exploded with a ringing report. Upon examining the two rails, that on which the powder had been placed was found to be simply blackened by the smoke. The other bad a piece lOin. in length and 2in. depth blown out of its foot, into fragments, none of which could be found, whilst the rail itself had been so bent by tbe bthofraoteur that it showed a camber of half an inch at tbe centre. This was considered a very satisfactory test, and it showed, moreover, that lithofructcur is well adapted for use in vertical boreholes, its action being intensely local. A very good test of the special adaptability of lithofracteur for sub-aqueous opera tons was afforded by tbe demolition of a portion of a mass of rock lying to the south-east of the Hermitage. Hei c a charge of 1001 b. of the compound was inserted at the far end of a fissure 19ft long, measured from tbe fr mt, and 20ft deep measured from the top. One side of this fissure consisted of the main body of tbe rock, and the other of a rocky wall of the length and depth just stated, and 12 ft. thick. The exploding charge consisted of 10 lb. of litbofracteur, and in it two capped fuses were inserted. The charge was laid during the afternoon of Saturday week, the intention being to fire it at 9 p.m., when there would be about 12 ft. of water over it An attempt was made at that hour by Mr. Nursey to land on the rock ; which, however, proved ineffectual, in consequence of there being a heavy sea on. The charge, therefore, had to lie under water during Sunday, and on Monday morning a landing was effected at high water and the fuzes were ignited, but did not burn down to the charge. It was afierwards discovered this was owing to their having become chafed against the rocks from long exposure to action of the wind and waves. At low water tbe same afternoon a 51b. capped charge was placed between tbe former exploding charge and the boxes containing the 1001 bof lithofracteur, and the fives were well covered and led up the rock, the charge being properly.protected against the heavy seas which washed up tbe fissures, At ten p.m. a landing was effected on the top of the tide, and the fuzes were fit cd. The operators then regained tbeir boat and were rowed to a safe distance, and in about twelve minutes — the fuze having been properly timed to admit of the retreat—- a heavy explosion took place, a cloud of spray being thrown high up into tbe air and showing distinctly against a clear sky. Although it was night and tbe weather anything but propitious, a number of persons had assembled on the Victoria and Albert piers, from which thuy very distinctly saw the effects of the explosion. A return to the scene of operations, and a row round tbe rock disclose i the fact that the massive wall of rock had been cleared, away, tbe explosion having done its work very effectually. The rock weighs two tons, to the cubic yard ; taking, therefore, the dimensions of the wall as given above, it follows tbat tbe total weight of rock removed by 1151 bo£ lithofracteur was 340 tons. The result proved that the lithofraoteur was none the worse for 55 hours of exposure to wind and waves, and tbat the action of five successive heavy tides had in no way effected it. The satisfactory manner in which the lithofracteur acted in all cases has led Sir John Coode to resolve upon using it as a blasting agent in carrying out the new works.

Its use iit New Zealand. — The value of lithofracteur is beginning to make ifcaelf felt on the Coroinandel goldfield. Mr. R. F. Luks, of the Tokatea, obtained a quantity some time ago, and it has been used with great success in the Van mine. The manager of the Tokatea, Mr. Rr. Kelly, has been trying experiments with this explosive agent, with a view to satisfying himself whethw he could recommend its general employment to his directors, and has come to the conclusion that he can do so. He took a charge of two ounces of lithofracteur; and placed it on a perfectly solid block of stone, weighing about a quarter of a ton — simply covering the charge over with a handful of wet clay. When fired, the charge split the stone into two pieces, and so shattered the two halves that they would be easily broken up with the hammer. The advantages, he states, are, that when for powder a bore-hole lf-th of an inch is required, for the lithofracteur the bore need be only one inch, thus reducing the labor, and that the bore : hole need not be carried bo far into the stone for one compound as for the other. This is a great saving hxlabor.. Again, the lithofracteur requires no tamping to charge, being simply covered with wet clay, water, or even sand ; and should the charge miss fire it can be removed and renewed with perfect safety. Mr. Kelly confidently recommends its use to the company. — " New -Zealand Herald."

We are informed that this new compound'] is now in use at the railway works at Manuka I Creek.— [Ed. •• T.T."J