SUBAQUEOUS EXPLOSIONS.] UNDULATORY FORCES. ELECTRICITY. 



193 



Ksperiment 44. A cartridge, closed at one end, and 

 well pitched over, to render it water-tight, is to be filled 

 Fig. 52. with gunpowder, and into it may be 

 fitted a cork, through which two thick 

 copper wires have been passed, their 

 BMMJIH inner ends being joined together by a 

 I fine iron or platina wire, as represented 

 I in Fig. 52. Tut! iron wire thus rests in 

 I contact with the powder. The conduct- 

 ing wires are attached to the coarse 

 wires of the cork, and their other ends 

 HHB| are laid near the battery. The cartridge 

 is then to be sunk into a pail of water, 

 or a pond, and one of the wires may 

 QI^HV be connected with one end of the bat- 

 tery. On the other wire being brought 

 into contact with the battery, the cur- 

 rent at once passes ; the fine wire in 

 the gunpowder becomes ignited, and an 

 explosion at once ensues. The mode of carrying out 

 this experiment is illustrated in the following engrav- 

 ing; in wliich each part of the arrangement is fully 

 shown. 



Fig. 53. 



This experiment has had an extensive application for 

 the purposes of warfare, <tc. ; to which we have already 

 alluded iu general terms. We may here more particu- 

 larly mention some instances of the kind. 



Lhiriugthe Russian war, " infernal mach'nes," of two 

 sorts, were employed by the Russians. One kind of 

 these exploded whenever a vessel touched one part of 

 the arrangement. At the top of a conical vessel, nearly 

 filled with gunpowder, a tube was placed, which contained 

 a glass one, holding sulphuric acid ; external to which 

 was chlorate of potass mixed with sugar. When a vessel 

 struck the tube, the acid fell on to the chlorate mixture, 

 ami, igniting it, soon exploded the powder. These 

 were, however, very uncertain in their action, 

 ami were superseded by an arrangement in which voltaic 

 electricity was employed as the igniting agent. The 

 plan adopted was precisely similar to that described in 

 our last experiment. The "infernal machine" was 

 sunk in the course which vessels were expected to take; 

 and inside, next to the gunpowder, were two wires, 

 across which was stretched a finer wire. From the main 

 wires two long conducting wires extended to the shore, 

 thi! ends being placed in close proximity to a voltaic 

 battery. A person was kept watching the progress of 

 any vessel ; and when the latter had arrived over the 

 "infernal machine," contact was made with the battery, 

 and an explosion either actually took place or ought to 

 hav done so. There is, however, a wonderful difference 

 between trying experiments at the lecture-table, and 

 carrying them out on a large scale. This fact the 

 ians fniind out to their cost; and, practically 

 speaking, these voltaic "infernal machines" were utterly 

 worthless. 



For engineering and mining purposes, in wliich every 



arranguui'.-iit can be made as complete as possible before- 



ainl not necessarily expose I to any chance of 



disarrangement, tliis plan of igniting gunpowder for 



VOL. I. 



blasting, <fec., is of the utmost value. Any amount of 

 powder may be discharged simultaneously. There is no 

 risk of the explosion occurring before proper precautions 

 have been taken, because the whole arrangement is 

 subject to the will of the superintendent. The instant 

 the command to "fire" has been given, the effect takes 

 place ; and hence no accident need occur. 



As an instance of such an application of voltaic electri- 

 city, we may mention the removal of many thousands of 

 tons of chalk from the clifl's of Dover, during the 

 formation of the South-Coast line of railway. Chambers 

 were made in various parts of the rock, and these were 

 filled with gunpowder. Each was connected, by means 

 of wires, with the large battery placed at a considerable 

 distance from the charge : when connexion was made with 

 the battery, the explosion instantly took place. 



Colonel Pasley first proposed to apply voltaic electri- 

 city for the purpose of blowing up sunken vessels ; and 

 this plan has been most successfully adopted in many 

 cases. It is much to be regretted that our miners adopt 

 the old and uncertain plan of the common fuse, which is 

 highly dangerous, and is the frequent cause of loss of 

 life. Generally speaking, nothing is more difficult than 

 the introduction of any new invention ; and just in 

 proportion to its value, so the prejudice against it 

 increases. We once met with an old miner, whose chief 

 objection to the use of voltaic electricity, for blasting 

 purposes, was its great safety; for he argued, that a 

 diminished risk would tend to lower the wages of the 

 men. 



A very ingenious application of voltaic electricity has 

 been made by Mr. Hart, an optician, and philosophical 

 instrument-maker, of Edinburgh, for the purpose of 

 lighting chandeliers, and other gas arrangements which 

 are inaccessible by ladders. He arranges over each 

 burner two main conducting wires, connected by means 

 of a fine platina wire. On the ignition of the latter by 

 the voltaic battery, the gas is simultaneously lit in each 

 burner ; and by means of an electro-magnet, the platina 

 wire is instantly removed from the flame when the 

 latter is produced. This, of course, prevents the de- 

 struction of the platina by the impurities which coal 

 gas always contains. The experiment may bo easily 

 repeated by means of a single gas-burner: indeed, a 

 tallow candle may be readily ignited by a wire heated 

 white-hot by means of the voltaic battery 



THE CHEMICAL EFFECTS OF VOLTAIC 

 ELECTRICITY. 



As this subject will be fully dealt with under the heart 

 of Electrotyping, we shall confine our remarks to the 

 pure philosophy of the question ; and so prepare our 

 renders to enter into those details which the applications 

 of any branch of science always afford. 



We have already stated, that a voltaic battery, or 

 the single cell, depends for its action on tho fact that 

 chemical decomposition takes place in some part of the 

 arrangement; and to this is due the evolution of free 

 electricity. If the terminals of a single pair of plates, 

 or of one cell of any form of the voltaic battery, be 

 immersed in a solution of any salt, the acid always 

 passes to one side, and the base to the other; and 

 this is so universally the case, that definite laws, of 

 what has been termed electro-chemical decomposition, 

 have been discovered, wliich govern every case in 

 which chemical changes take place in the presence of 

 free electricity. 



The simplest instance of the chemical effects of a 

 voltaic battery to which we can refer, is that of the de- 

 composition of water, which is a type of all electro- 

 chemical changes. For the purpose of trying the fol- 

 lowing experiments, four cells of Grove's battery, or tec 

 of Daniell's or Smee's, will be required ; and presuming 

 that the student has supplied himself with any of these 

 arrangements, we shall proceed to investigate some in- 

 teresting phenomena. The wires proceeding from tho 

 battery should be connected with a piece of platina foil ; 

 because, as that is unacted on by most of the substances 



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