OS THE ELECTRIC COLUMN, 



167 



room. I made use therefore of the little table above-men- 

 tioned, for placing on it additional columns, which I made 

 upright like the common pile, as more easily managed; 

 and knowing that with the same number of groups, the 

 strikings would be accelerated by larger plates, but that it 

 was a long and tedious operation to cut them round, I de- 

 termined to make a co/mwih with square plates. For this Sheets of zii?.; 

 purpose I bespoke some sheets of luminated zinc about the "°' smooth, 

 thickness of a card ; but those which I received were so 

 much puckered, that I despaired of their being fit for my 

 purpose; however I obtained flat plates of them by a 

 method which it may be useful to explain. 



I procured a good pair of hand-shears, and with these I t)ut may be 

 first cut the puckered sheets into slips of \\ inch breadth, ^ronV°pres- 

 as nearly as they could be traced upon such an uneven sure. 

 surface; and placing many of these slips upon one another 

 betw^een two pieces of hard wood, I pressed them with force 

 in a vjce, leaving them there for half an hour: they came 

 out very flat, on'y not very straight, but this could be 

 mended. Zinc, in this malleable state, having nearly the 

 softness of lead, stretches laterally by that great pressure, 

 and thus the puckerings are effaced. Making then straight, 

 with a file, one side of the slips, I marked on this edge, 

 with a divider, points at I^ inch distance; and by thes* 

 points I traced with a square the plates to be cut with the 

 shears: these pieces were distorted by the cutting; but 

 placing them also over one another, by scores, between two 

 thick plates of brass, and pressing them strongly in the vice, 

 they became flat; and I had only to round a little the 

 angles with a file, placing them again in the vice without 

 the brass plate. 



In this manner, I made 300 2</ic plates If inch square, An upright 

 and having cut an equal number of pieces of Dutch-gilt^ "^^ '''*" 

 paper o^ the &^\r\e size, I mounted this upright co/if»j7i be- 

 tween 4 glass rods covered with sealing-wax, fixed in a 

 wooden base. This column, loose between the rods, is sup- 

 ported at the bottom on 4 insulating pillars if inch high, 

 on which is first laid a brass plate with a projecting part of 

 about 2 inches, at the extremity of which is a large hole for 

 receiving the end of proper conductors; and for the same 



purposcj 



