48 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
The main point of such improvement lies in the con- 
nections between rail and rail. If the resistance of the 
bonds and their contacts were negligible there would Dbe 
very trifling stray currents. 
For example, if we are dealing with a double track of 
ninety-pound rail, the resistance is about 45 ohm per 
thousand feet or .0087 ohm per mile. Such a structure 
could carry 1ooo amperes with a loss of but 8.7 volts 
per mile and should reduce the stray currents to a very 
minute percentage since the resistance is not only very 
small compared with any probable value of the earth 
resistance between track and pipes, but also very small 
compared with the resistance of the pipes themselves in- 
cluding their bad joints. With, say, one per cent of the 
current in the earth conductors the electrolytic action, 
while not absolutely suppressed, would be so slow and so 
trifling as to be scarcely worth considering save at a few 
points which could be protected if necessary. 
All this points to the necessity of the most perfect 
bonding, as before pointed out. All sorts of devices have 
been tried. ‘T'wo of the most ingenious, aside from those 
already referred to, consist respectively of a plastic con- 
ducting film squeezed between the bond surface and the rail 
surface, and of a heavy copper dowel pin driven into a hole 
in the end of one rail and the other rail forced upon it and 
held with the fishplate. ‘The uncertain point about these 
as about many other bonds is their ability toendure jarring 
and corrosion. Bonds are sometimes subject to the same 
sort of electrolytic action just mentioned in connection with 
pipe joints. 
The most radical cure for joint resistance of rails may 
be found in the two now familiar processses for making 
continuous rails. ‘T'hat a continuous rail is entirely feasi- 
ble mechanically now admits of no dispute. Fxpansion 
does not and cannot take place longitudinally when rails 
are firmly embedded in paving, even under the extremes of 
temperature encountered. Whatever yielding there is, is 
lateral, and the track is not thrown out of line.