1.S39.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



289 



both attaflieil to tlu' s;ime 2-ini-h rope, being previously covered with 

 t;ipe anil coated with waterproof composition, and the rope itself being 

 previously saturated with boiling tar, after which they were all bound 

 round together with broad tape, coated whh the same waterproof 

 composition, and served round with hemp yarns. Thus the whole had 

 the appiMrance of a single rope, oval in section, capable of being coiled 

 up, which was done upon a drum of 4 feet in diameter. This pre- 

 caution was found absolutely necessary to prevent kinks in the wires, 

 and the arranginnent of saturating the rope wilh tar was also found 

 necessary, to prevenl its contractions and expansions between wet and 

 dry from breaking the joints of the copper wire. At the far end, 

 where the wires were to be introduced into the charge, they were 

 separated for a few feet in length into a fork. The case containing 

 the jiowder was a tin cylinder made for the purpose, and just capable 

 of holding the proposed charge of 10 lbs. ; but to prevent the loss of 

 the whole charge in ctase of accidents, a small canister capable of con- 

 taining about i lb. was introduced into one end of this cylinder, with a 

 perfectly sound and strong metallic partition between the two. This 

 small canister was called the priming-box, and two short copper wires, 

 called the priming wires, were led into it, the ends of which were 

 connected inside by a piece of platin\nn wire about an inch long. These 

 wires nnist only be in contact with wood, ta]ie, or canvass, and there- 

 fore the priming-box had a wooden lid, through which these wires 

 passed, but the rest of it was usually made of tin. In immediate con- 

 tact witli the platinum wire, mealed powder was used, but the rest of 

 the powder in the priming-box was common large-grained powder. 

 Colonel I'asley rejected on trial two sorts of fulminating or detlagrating 

 powder, tliat had been used, one by Mr. \Vm. Snow Harris, of Uevon- 

 port, and the other by Dr. Hare, of fhiladel)ihia, because he found no 

 superiority in either of these over mealed powder. He also rejected 

 iron wire on trial, because the platinvnii wire tired gunpowder with 

 three cells of Daniell's battery, whereas the iron wire reijuired four to 

 etfect the same object. To secure the entrance of the copper wires 

 into the prinung-box, by a water-proof composition, elastic enough 

 neither to be cracked nor deranged by those strains or pressures, which 

 cannot be entirely got rid of under diHicult circumstances, ami at the 

 same time to pre\ent a pull upon the copper wires from without 

 breaking the very delicate platinum wire fixed to their ends inside, 

 were objects, the attainment of which gave infinite trouble. The ex- 

 pedients usually reconmiended, of corks coated with sealing-wax, for 

 the copper wires to pass through into the charge, and hidia-rubber 

 tubes, or varnish, to insulate tlie remaining length of eacli copper con- 

 ducting-wire, were rejected ; the former as being fit only for a lecture- 

 room, and the latter as being too expensive : instead of which pitch, 

 softened by liees-wax and tallow, was used at the suggestion of .Ser- 

 jeant-Major Jones, who had tried a great number of experiments for 

 ascertaining the best sort of water-jiroof compositions for bags of gun- 

 jiowder in lb32, when Bickford's fuses were first used by the corps at 

 Chatham, antl who also, at the same period, discovered tlie means of 

 imitating those fuses in an efficient mamier. 



" Such being the preparations, the sham wreck, which was a small 

 rough fir-vessel, 5 feet long, 34 feet wide, and 24 feet deep, was simk 

 at low water, opposite to Chatham gun-wharf, on the 23rd of March, 

 the day appointed for this final experiment, having a ring and lines 

 attacheil to it, which were supposed to have been fixed by a diver, 

 the ends of which were kept in a six-oared cutter, ha\ing on board 

 the voltaic battery, the coil of conducting wires on their drum, and 

 the charge of powder, which was attached to them by fixing their ex- 

 treme ends to the priming-wires before described, and covering the 

 joints with tape and water-proof composition. As soon as the sup- 

 posed wreck was sunk, the charge was lowered and hauled into its 

 place in perfect contact with one side of the wreck, by means of those 

 lines, and the end of the downhaul was then made fast in the boat to 

 the couducting-rope and wires, so much of the latter having been 

 veered out and sunk, as- was necessary to allow the charge to reach 

 the bottom. All this having been done at slack-water, and conse- 

 quently withoid, any obstruction from the current, the boat was moored 

 nearly over the spot, and reiuained there for several hours, mitil the 

 period appointed for the explosion, when the flood-tide was running 

 strong, and the depth of water over the' charge about 30 feet. At the 

 hour a|)poiiited, a great imnd)er of spectators being assembled on the 

 wharf opposite, the cutter warped upon her cables against the tide, 

 until the full extent of SOU feet of tlie conducting wires was veered 

 out, after which Captain Sundham, the executive officer in the boat, 

 made the signal by bugle that all was ready, one of tlie cimducting 

 wires was now comiected with one pole of the battery, on which 

 Colonel I'asley, who was amongst the spectators on the wharf, gave 

 the order also by sound of bugle to fire; and ;ls soon as llu? last note 

 of this sound was heard, the second conducting wire was brought in 



contract with the second pole of the battery, and immediate explosion 

 took place. A brisk shock was instantaneously felt and a dull sound 

 heard c'l the wharf ; in a few seconds after which a small column of 

 water was thrown up, followed immediately by all the fragments of 

 the sham wreck, which, being separated by the explosion, lioated up 

 to the surface. On the same occasion, some small charges were also 

 fired at the bottom of the Medway, one of which having been kept ten 

 days in a bucket of water, before it was sent down to the river, proved 

 the efficiency of the Serjeant-Major's composition. The successful 

 result of this experiment, not so interesting to the spectators, was felt 

 to be of equal importance with the former, and had been looked for- 

 ward to with still greater anxiety. 



"On the (Jth of April, Colonel Pasley blew two large hard sandstones 

 to pieces at the bottom of the Medway, one by one charge, the other 

 by two successive explosions, each charge consisting of J lb. of powder. 

 The holes were 3 inches in diameter, and the charges were contained, 

 one in a tin cylinder of a diameter to fit the hole, the two others in 

 cylindrical canvass bags of the same size. Over each charge was 

 placed a wooden cone, and the up]jer part of each hole was tamped 

 by small broken stones, on Mr. Howe's principle before described. 

 One stone being of a compact form was split into five pieces by the 

 explosion; the other being much thinner, and consequently having 

 little resistance eitln-r above or below the hole, the first charge only 

 blew out the bottom of the hole below and the tamping above. This 

 stone was therefore got out of the water, and the second charge put 

 into the centre of the hole, having its own wooden cone over it, whilst 

 one of the two cones previously used, which had floated up to the 

 surface, was introduced under it, and then the hole was tamped both 

 above and below this second charge, which, on the stone being again 

 lowered to the bottom of the river, was fired by the voltaic battery, 

 and the stone was thereby broken into three pieces. In this experi- 

 ment all the prejiarations were made on the wharf-wall of the Gun 

 Wharf, from whence the stones, when loaded, were let down to the 

 bottom of the pier near it from a crane, and the slings used in this 

 operation were not disengaged before either of the explosions, which 

 enabled the men employed to get up the second stone, after the ex- 

 plosion of the first charge loifged in it, which had not broken the 

 slings. These blasts were fired from the wharf, where the voltaic 

 battery was placed, with conducting wires 60 feet long in two of the 

 experiments, and 100 feet long in the third, which being of common 

 bell-wire, only about one-sixteenth of an inch in diameter, required no 

 less than eight cells of Uaniell's constant voltaic battery to produce 

 ignition, although the same number (jf cells will fire powder under 

 water at five times that distance with the larger wires before described. 

 These experiments in blasting rock under water were tried in reference 

 to the important object of removing obstructions in rivers or in har- 

 bours, by blasting with the voltaic battery, in which case the holes in 

 the rock would require to be previously prepared, and the charges in- 

 troduced into them, by means of the diving-bell. Numerous experi- 

 ments were also tried for firing several charges simultaneously by the 

 vcjltaic battery, but the results were not satisfactory, as the engineers 

 at Chatham were never able to fire more than two or three charges 

 simultaneously, at any respectable distance; but they have not seen 

 reason as yet to ascribe their disappointment to the fault of the bat- 

 tery, but to the circumstance, that having no more than 500 feet of 

 the large conducting wires, they were obliged, in all their attempts at 

 simultaneous explosions, to make use of the small common beU-wires, 

 which they found by direct comparison not to be capable of conduct- 

 ing the same intensity of voltaic electricity to more than about one- 

 fifth of the distance to which it could be conveyed by the larger wires 

 of about three times their diameter. Accordingly, the ofticers present 

 at these experiments think that it would be perfectly impracticable to 

 fire a charge of gunpowder under water by a voltaic battery composed 

 of six of Daniell's large cells only, at the distance of 300 or 400 yards 

 by using common copper bell wires as the conducting wires, according 

 to an opinion given in a paper published in the "Civil Engineer and 

 Architect's Journal," for the month id' May, 1S3S. From their own 

 experience, they consider that gunpowder could not be fired at the. 

 last-named distance, by such conducting wires, with any battery com- 

 posed of fewer than 90 of Professor Daniell's largest cells, whiili 

 would probably be a more powerful voltaic battery tlian has ever yet 

 been used by man. 



" On the 17th of April, Colonel Pasley repeated one of Mr. Wm. Snow 

 Harris's experiments before alluded to, by causing the wires from his 

 voltaic battery to pass through two barrels full id' gunpowder, and two 

 small charges of 5 lbs. each, the latter being jnovided with small pla- 

 tinum wires for explosion, whilst the cojipiu- wires passed straight 

 through the former in tlieir bright state, but the holes, which hail pre., 

 viously been bored in opposite staves of the barrel, for admitting those 



X 2 



