74 Uoyal Society :— 



and f inch thick, of which about 2000 are in daily use on the South 

 Eastern Railway, and the greater portion of these are now platinized. 

 The plates are delivered to me in their crude state, that is to say, 

 they are merely cut into form. Immediately on arrival they are 

 placed in a stone pan, and covered with a mixture of 1 sulphuric 

 acid + 4 water, in which they are allowed to remain for three or 

 four days or more. They are taken out as required, and are washed 

 under a tap of running water ; this operation dissolves out any foreign 

 matter that might be pernicious in a voltaic combination wherein 

 sulphuric acid was employed ; they are then partially dried. A hole 

 for a rivet is next drilled in the middle, near the top of each plate — 

 a belt of varnish one inch wide is applied to the top on both sides of 

 each plate — a blank one inch square, having the rivet hole for its 

 centre, being left unvarnished on each side — electrotype copper is 

 then deposited on the blank square in the usual way. The deposited 

 metal is then tinned, no part of the copper being left bare ; a con- 

 necting slip of copper, 6 inches X 1 inch is prepared and also 

 entirely tinned ; this is riveted to the graphite plate with a copper 

 rivet, also tinned. The soldering iron is now applied, and a little 

 solder run in between the two surfaces. By thus protecting all the 

 exposed copper with tin, the formation of sulphate of copper and its 

 attendant inconveniencies are prevented. The plate is now platinized. 



A mixture of 1 sulphuric acid + 10 water is placed in a vertical 

 glass cell, to this are added a few crystals of chloride of platinum till 

 the solution presents a faint straw colour. The battery power em- 

 ployed for platinizing is three cells of platinized graphite and zinc. 

 The positive electrode is platinum or graphite itself, and is presented 

 to both sides of the plate that is to be platinized. The action is 

 allowed to go on for about twenty minutes. Each finished plate is 

 tested as to its power of liberating the hydrogen of electrolysis, by 

 placing it in acid water in contact with an amalgamated zinc plate. 



I have drawn out the above description in the presence of our 

 assistant, who attends to this department of the telegraph establish- 

 ment, in order to be correct in the small details. 



The battery-cells for the plates above described are quart jars of 

 stone-ware that resists acid. The exciting solution is 1 sulphuric 

 acid + 8 to 12 water. Zinc plates are riveted to the other end of 

 the copper connecting slip, also with tin rivets. The zinc is strongly 

 amalgamated. It is dipped in a vessel containing 1 sulphuric acid 

 + 4 water, and after a few seconds, more or less, is withdrawn and 

 thrust in its then condition into a trough of mercury, and set aside 

 to drain. On the following day it is treated in a similar manner. 

 When the batteries are being put together, and before the zincs are 

 placed in the jars, the foot of each is placed in a trough or slipper 

 of gutta percha, 3 inches by i inch, containing about a couple of 

 ounces of mercury. A battery thus carefully prepared will stand for 

 an indefinitely long period with little perceptible waste, and be ready 

 for use at all times. Under ordinary circumstances it is not neces- 

 sary to dismount the batteries employed for telegraph signaling 

 more than once a year. Mercury is added during the interval, and 



