Q. I am at work on a lead-lined tank, which is used only in the summer season. In the fall the water is allowed to run out, and it remains empty over winter, but in running out there remains about half an inch of water over the bottom of the tank, and this is allowed to dry out. This spring when I examined the tank I found the bottom eaten full of holes varying in size from the point of a pin to an inch opening. I never saw anything like it before in sheet-lead, and would be much obliged if you would give me an explanation of it. The water used is very hard water and heavily impregnated with lime.

A. The fact that the water contains lime-salts would not account for the holes in the bottom of the tank. The presence of carbonate of lime in the water would tend to form an insoluble carbonate of lead on the surface covered by the water. It is possible that the holes were produced as the result of some galvanic action between the lead and some other metallic substance - either an impurity in the lead itself or another metal accidentally left in contact with the lead.