38 

 ON A SIMPLE AND CONVENIENT FOEM OF WATER BATTERY 



[American Journal of Science [3], XXXI21, 147, 1887 ; Philosophical Magazine [5], 

 XXIII, 303, 1887 ; Johns Hopkins University Circulars, No. 57, p. 80, 1887] 



For some time I have had in use in my laboratory a most simple, 

 convenient and cheap form of water battery whose design has been in 

 one of my note-books for at least fifteen years. It has proved so useful 

 that I give below a description for the use of other physicists. 



Strips of zinc and copper, each two inches wide, are soldered to- 

 gether along their edges so as to make a combined strip of a little less 

 than four inches wide, allowing for the overlapping. It is then cut 

 by shears into pieces about one-fourth of an inch wide, each composed 

 of half zinc and half copper. 



A plate of glass, very thick and a foot or less square, is heated and 

 coated with shellac about an eighth of an inch thick. The strips of 

 copper and zinc are bent into the shape of the letter IT, with the 

 branches about one-fourth of an inch apart, and are heated and stuck 

 to the shellac in rows, the soldered portion being fixed in the shellac, 

 and the two branches standing up in the air, so that the zinc of one 

 piece comes within one-sixteenth of an inch of the copper of the next 

 one. A row of ten inches long will thus contain about thirty elements. 

 The rows can be about one-eighth of an inch apart and therefore in a 

 space ten inches square nearly 800 elements can be placed. The plate 

 is then warmed carefully so as not to crack and a mixture of beeswax 

 and resin, which melts more easily than shellac, is then poured on the 

 plate to a depth of half an inch to hold the elements in place. A frame 

 of wood is made around the back of the plate with a ring screwed to 

 the centre so that the whole can be hung up with the zinc and copper 

 elements below. 



When required for use, lower so as to dip the tips of the elements 

 into a pan of water and hang up again. The space between the ele- 

 ments being -fa inch, will hold a drop of water which will not evaporate 

 for possibly an hour. Thus the battery is in operation in a minute and 

 is perfectly insulated by the glass and cement. 



This is the form I have used, but the strips might better be soldered 

 face to face along one edge, cut up and then opened. 

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