164 Account of some Eleclrkal Experiments. 



one was adapted to t!ie purpose of these experiments for the. 

 occasion, and by a simple mechanical arrangement was made 

 equal in charging- power to the large one. 



The joint action of these machines enabled us to charge the 

 whole battery of 75 feet coating in two minutes; and this rate 

 of charging was maintained through the whole of our experi- 

 ments. 



The metallic cylinders were all of the same size ; namely, six 

 lines diameter, and 24 lines high, with a bore of 2^ lines dia- 

 meter and 18 deep. We were provided with two of each of the 

 following metals, — Bismuth, zinc, tin, lead, iron, copper, and 

 brass. A steel wire or needle, about the 40th of an ir.ch thick 

 and three inches long, was then coated with wax in two places, 

 to such a thickness as to admit of its sliding freely into the bore 

 of either of the cylinders. The length of the needle was then 

 prolonged by the addition of a piece of leaden wire vroth of an 

 inch diameter and nine lines long to its lower extremity, in close 

 contact with which it was secured by the same wax. Fig. 1, 

 Plate III, represents this needle. W is the fine leaden wire, 

 and CC the coatings of wax. All the precaution necessary in 

 preparing such needles, is to place the wax round them with 

 care, so as to keep the needle in the centre of the metallic cy- 

 linder when it is placed therein, dining which process it is ne- 

 cessary to keep the leaden wire as straight as possible, that its 

 end may rest on the bottom of the cylindrical cavity without ap- 

 proaching any where in contact witii its sides. Several of these 

 needles may be prepared before tb.e commencement of the ex- 

 periments, as it is necessary to employ a fresh one at every ex- 

 plosion. Fig. 2 represents one of the cylinders; its cavity (which 

 is shown by dotted lines) is to be filled with water or oil, and a 

 needle prepared as above, introduced carefully into it until the 

 point of the leaden wire rests on the bottom of the cylinder. To 

 prevent the oil or water from being thrown al)Out, the cylinder 

 should be placed in a wooden box, open on one side and lined 

 with lead at bottom: 'the bottom being connected with the out- 

 side of the battery, a communication is made by a wire, between 

 the upper part of the needle and the receiving ball of Cuthbert- 

 son's di>-charging electrometer, the electrometer being connected 

 with the inside of the battery. This arrangement is shown in 



fig- '^- . . 



In this disposition of the apparatus, a cylinder of bismuth 

 filled with water was subjected to the action of the battery of 

 75 feet, charged to 1 5 grains. A single explosion shattered it to 

 pieces, and dispersed the parts to a distance with considerable 

 violence. 



Another cylinder of bismuth the same size as the preceding 



wa* 



