74 The Rev. Dr. Callan's Experiments on the 



from it without the smallest risk of injury, and by which the 

 full decomposing eflfect of a battery of a hundred or five hundred 

 pairs, arranged in one series, may be produced without exhaust- 

 ing the power of the battery more rapidly than if it contained 

 only three or four cells. Thirdly, a new negative element far 

 cheaper, far more durable, and one which may be made to act 

 more powerfully than the platinized silver used in Smee's bat- 

 tei-y. Fourthly, a new mode of protecting iron against the 

 action of the weather and of various corroding substances, so 

 that iron thus protected may be used for all the purposes to 

 which sheet lead and galvanized iron are applied. Fifthly, a 

 method of producing a brilliant intermittent lime light by means 

 of a small galvanic battery. Sixthly, a new mode of exhibiting 

 the dissohang views by means of the lime light. Lastly, a new 

 sine galvanometer, which is the only instrument yet made by 

 which very powerful galvanic currents can be measured. 



The first result was a new apparatus for applying with perfect 

 safety the mixed gases to the production of the oxyhydrogen 

 flame and lime light. In my first experiments on the decom- 

 position of water, I made use of a glass vessel containing dilute 

 sulphuric acid and four parallel plates of platinized platina, each 

 having a surface of about 14 square inches. The mouth of 

 the vessel was stopped by a thick piece of wood, through which 

 the wires from the electrodes passed. In this wood was cemented 

 a tapped brass nut to which a stopcock and Hemmiug''s jet 

 might be screwed ; the mouth of the vessel was made air-tight 

 by cement. I soon found that with a glass vessel the use of 

 Hemming's jet was unsafe. On one occasion, when I employed 

 twenty 6-inch cells of our cast-iron battery, the Hemming's jet 

 did not let out all the gases produced in the vessel ; for after 

 breaking the connexion between the battery and electrodes, the 

 gases continued for some time "to issue from the jet and kept up 

 the lime light, although the battery had not worked for more 

 than a minute or two. Had I allowed the battery to work nine 

 or ten minutes, the gases would have been condensed within, 

 and would have burst the vessel ; I therefore saw that I must 

 either get the gases separately, or devise some means by which 

 the mixed gases might be safely inflamed, and might at the same 

 time pass without much resistance from the glass vessel. I 

 attempted both. To get the gases separate, I put a plate of 

 porous earthenware between the electrodes so as to form two 

 air-tight cells. 1 thus succeeded in obtaining the gases separate ; 

 but finding so much difficulty in making the cells air-tight, I 

 gave up the idea of looking for the gases separately. In order 

 to avoid dangerous explosions in igniting the mixed gases, and at 

 the same time to allow them to pass freely to the jet, I sent them 



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