plication to old work is almost prohibited by the attendant expense.
Attacking the problem from a directly opposite standpoint, there seems to be a chance of successfully invoking the aid of some purely chemical method of rendering lead and iron innocuous, electrolytically
Lead Service Pipe illustrating the Local Effects of Eight Months' Electrolysis. The other side of this pipe is smooth and clean.
speaking. If we can obtain an insulating oxide, lacquer, or varnish that will retain its high-resistance properties during the ordinary lifetime of the buried metal, it will be possible to effectually protect pipes and cable coverings by coating them prior to burial. Or, if we can stumble upon an electrolysis-proof alloy, formed by the addition of a few per cent of some foreign metal to the pipe material during manufacture, the buried conductor will need no protection whatever.
But, supposing that we discover this lacquer or this alloy and by such means guard against damage to all new construction, how are we to care for the metals already buried? We can not dig them all up and paint them, neither can we attempt to replace them by the new alloy. I do not see that the state of the art to-day presents any solution of the difficulty, other than the banishment of the single trolley system. None of the electrical remedies (so called) offers more than partial and temporary relief, and the chemical field is just beginning to be explored.
Permit me to state most emphatically that this is not intended as an argument in favor of the abolishment of single trolley systems. Our civilization owes more to them than could be rehearsed in catalogue form within the limits of one issue of this magazine. We have nothing at present that can be employed as a satisfactory substitute for the ordinary electric railway. The underground trolley is a safe substitute, but the great expense of installation renders it available for very few localities. The overhead trolley,
