100 



diameter were secured to a slip of window glass half an inch wide 

 and four inches long, so that they rested upon the flat surface of the 

 glass, leaving an interval between their points of one-twentieth of 

 an inch. The wires were connected, one with the negative con- 

 ductor of a powerful machine, the other with a ball to receive sparks 

 from the prime conductor. On placing the glass in a flat dish filled 

 with water and turning the machine, the glass between the points 

 soon became fractured, and after 100 revolutions the fracture 

 enlarged and two small cracks appeared. After 200 revolutions an 

 excavation was formed, but on the side opposite to that on which 

 the wires were tied. After 250 revolutions the glass was completely 

 perforated. Many variations of this experiment were made, in all 

 of which the same kind of mechanical effect was obtained. Even 

 quartz was excavated*." 



It being thus shown that a lateral disruptive action takes place 

 within a certain distance of the seat of discharge, the idea at once 

 suggested itself to me, that by using two parallel wires separated at 

 their extremities like those in Mr. Crosse's experiment, and similarly 

 connected with an electrical machine or Leyden jar, bringing their 

 ends in contact with the surface of a calculus, and then allowing a 

 series of moderate discharges to take place between the extremities 

 of the wires, a disintegrating effect would be produced upon urinary 

 calculi of the same nature as that witnessed in glass and quartz. 

 And short of the actual disintegration of a calculus in the bladder 

 of a living person, the following experiments will, I trust, be deemed 

 conclusive on this point. 



Two copper wires, one-twentieth of an inch in diameter, were 

 connected, one with the external, the other with the internal surface 

 of a Leyden jar, having about 400 square inches of internal metallic 

 coating. These copper wires were soldered to platinum wires half 

 an inch long and one-thirtieth of an inch in diameter. Each wire 

 was drawn through a fine gutta percha tube, and the tubes, having 

 first been placed perfectly parallel, were warmed and gently pressed 

 together so as to assume somewhat of the appearance of a flexible 

 bougie ; the platinum wires projecting beyond the gutta percha to 



* Described by Mr. Walker in Lardner's Cabinet Cyclopaedia, vol. ii. pages 

 218-220. 



