Bache.] [April 17 



pathogenic, being received into a favoring host, so vigorously 

 form ptomaines, to their self-destruction as well as that of the 

 host, it would seem that, if upon issuing from as well as upon 

 entering a reservoir, the water were attacked in pipes from poles 

 all but encircling them, with an electro-motive force of a few 

 thousand volts, all germs must reach the denizens of cities sup- 

 plied from such a source, wholly innocuous, because they would 

 be dead. 



It need hardly be said that, if the poles were placed opposite 

 to each other on a heavy metal pipe convejang water, the elec- 

 tricity, seeking lines of least resistance, would not pass through 

 the water at all, but around it, through the great mass of the 

 pipe. But it should be obvious that it is easy to adapt to the 

 place of electrical attack of a pipe a simple contrivance consist- 

 ing of a section of the same diameter as that of the pipe, insu- 

 lating the poles from each other, and both from the general line 

 of the pipe. A plan that might at the first blush appear to some 

 persons better, as not entailing thus radically breaking the con- 

 tinuity of the main pipe, would be to have two series of metallic 

 insulated screws, representing by position two opposing arcs, 

 the individual screws of which should enter and pass through 

 corresponding holes in the pipe, the ends of the screws being 

 uninsulated. But this plan would not do at all. The experi- 

 ments described have proved the resistance of water to be so 

 great that a large volume of it is required for electricity to pass 

 easily through it. Consequently, in overcoming the resistance 

 of water in a metal pipe with poles attached, in the form of in- 

 sulated perforating screws, part of the electricity would, in 

 making large excursions, be received and conducted to the poles 

 by the metal of the pipe, instead of reaching them entirely 

 through the water. But, if the pipe were interrupted by a non- 

 conducting section, of length to be determined by the diameter 

 of the pipe and the electro-motive force to be used, then those 

 excursive lines of force would eventually fall into the determinate 

 direction of the poles entirely through the water. We see this 

 action clearly illustrated in the previous experiment, where, in 

 open vessels, resistance to the current rapidly diminishes as we 

 increase the volume of the liquid. We see the same thing also 

 clearly illustrated in the case of the hand submerged in the 

 ample basin of water, where the remotest abrasions of the skin 



