1840.] Boring Operations in Fort William. 685 



strands, over which a thick coating of pitch and grease was applied, 

 and then the two wires were lashed together by similar strands, 

 and again covered with pitch and tallow. A single rope, about 

 an inch in diameter, was thus formed, and on immersing the whole 

 in water, its action was tested, and a battery of twelve indifferent 

 plates sufficed to effect the ignition of powder. 



On the charge being placed in the cylinder, and the platinum 

 wire protected by means of a small tin priming tube, the plug was 

 driven into the collar. Over it, and for the purpose of preventing the 

 water forcing its way through the wood, a tin cap, having two holes 

 for the conducting wires to pass through, was carefully driven down 

 and soldered. In order to prevent this cap establishing a metallic 

 communication between the wires, and thus preventing the passage 

 of the galvanic fluid to the platinum wire, the diameter of the aper- 

 tures for the wires was made considerably larger than that of the 

 wires themselves, and the top of the plug covered with sealing wax. 

 The application of a red hot iron melted the sealing wax, and on the 

 cap being driven down it rose through the apertures and formed an 

 insulating collar round each wire. These arrangements being com- 

 plete, and the battery of 24 cells, 14 inches X 14 inches, in action, the 

 main conductors were connected to those of the cylinder, and the 

 insulating covering continued over the junction, when the cylinder 

 was lowered to the bottom of the bore. On its reaching this, the 

 circuit was completed, but no explosion followed, and on examination 

 it was found that from the smallness of the priming tube the plati- 

 num wire had come in contact with the metal, by which of course 

 its ignition was prevented. It was also found that though the 

 priming powder was dry, the water had reached the main charge, and 

 completely spoiled it. Further precautions being taken, several at- 

 tempts were made, but all with the same result, and it became evident 

 that the wrought iron case could not be rendered water-tight. Re- 

 course was then had to casting a cylinder of iron half an inch thick 

 throughout, and on trial this was found to be perfectly capable of 

 resisting the pressure of the water, and preserving the charge dry. 

 The first attempt with this failed from some unascertained cause, and 

 as it was thought possible that some portion of the conductor might 

 have come in contact with the iron tubing, an additional covering of 

 lashings, witli pitch and grease, was applied for a second attempt. 



4s 



