^ NATURAL PHILOSOPHY. 159 



by the action of the chemical menstruum in which it is immersed, and a 

 freshly-amalgamated, or new zinc lamina, is inserted into its place. The 

 capability of the piece-meal renewal of the consumptive element of the bat- 

 tery in this interpolator} 7 - and fragmentary way, is then the cause of its "per- 

 petual maintaining " power. 



It may be added that one of these perpetual maintenance batteries has 

 now been constantly at work for months in a large electrotyping office in 

 London, and has thoroughly established its reputation for unparalleled 

 steadiness, convenience and power. The battery is also unquestionably one 

 of the most economical that has ever been set to work, considering the 

 amount of service it is able to perform. It is calculated that the cost ofmain- 

 tainincj the ten-celled battery in operation at the terminal stations on either side of 

 the Atlantic, including all wear and tear, and consumption of material, loill not 

 exceed one shilling per hour. 



The flashes of light and crackling sparks produced on making and break- 

 ing contact with the poles of this grand battery, are very undesirable pheno- 

 mena in one particular. They are accompanied by a considerable waste of 

 the metal of the pole. Each spark is really a considerable fragment of the 

 metal absorbed into itself by the electrical agent, so to speak, and flown 

 away with by it. "When one of the poles of the battery is drawn two or three 

 times along the sharp angle of an iron instrument, like a pair of pliers, the 

 opposite end of the pliers being in contact with the other pole, the sharp 

 angle is shaved away in the midst of a shower of sparks, just as if some 

 irresistible and adamantine-toothed file had been carried along the same 

 course. As the signals of the telegraph will be constantly made by making 

 and breaking contact with the poles of the battery, these sparks would prove 

 very costly and troublesome, eating away the material of the contact-key, 

 and what is of more importance, very soon deranging its integrity and per- 

 fection as a mechanical means of communication and transmission. The 

 Electrician of the company has very nearly eliminated this difficulty by a 

 contrivance of considerable ino;enuitv. First he arranged a set of twenty 



/ O */ 



brass strings, something of the form and appearance of the keys of a musical 

 instrument, in opposite pairs, so that a round horizontal bar, turning pivot- 

 ways on its own centre, and flattened at the top, could lift by an edge either 

 of the sets of ten springs, right or left, as it was turned. This enabled the 

 contact to be distributed through the entire length of the edge, and breadth 

 of the brass strings, and the course of the current to be reversed, accordingly 

 as the right or left edge (the bar being worked by a crank handle) was raised 

 to the right or left set of springs ; the right set, it will be understood, being 

 the representatives of one pole of the battery, and the left set of the other 

 pole. By this arrangement four fifths of the spark were destroyed, simply 

 on account of the large surface of metal, through which the electrical current 

 had to pass when contact was completed. Still there remained enough to 

 constitute a very undesirable residue. This was disposed of finally, after 

 sundry tentative attempts, by coiling a piece of fine platinum wire, and plac- 

 ing it in a porcelain vessel of water, and then leaving this fine platinum coil 

 in constant communication with the opposite poles. As much electricity as 



