There are incorrect ideas as to how a bad heat-conducting material protects pipes from frost. Water absorbs and holds heat, but the heat is readily dissipated, or radiated, or becomes absorbed by cold air or substances with which it comes in contact, the consequence being that its temperature is reduced below 320 and the water becomes ice. The purpose of a bad heat - conducting material is to form a barrier to this heat transference, so that should the water be, say. 50 . the air and general surroundings can be much lower in temperature without reducing the heat of the water in any marked degree. The covering, therefore, does not afford any heat whatever, but prevents heat passing through it. Coverings, however, to be as effective as this would require to be of materials which are perfect non-conductors of heat, and this is not as yet possible. There are some very effective bad conductors, almost non-conductors, and the two best are undoubtedly hair felt and silicate cotton (slag wool). Both vary in effectiveness according to the thickness of the covering. If hair felt is used it can be 1/2 in., but | in. is better for good work. It should be cut in strips and he wound on the pipes soundly; but it is best not to bind it on too tightly afterwards. It should be secure, but not compressed.

The silicate cotton is usually a loose material, and requires to be placed in a casing. It can, however, be obtained sewn on to canvas Probably any one of the patent compositions used for jacketing steam boilers would answer the purpose. The coating should afterwards be lagged with narrow boards secured with iron belts or bands, or be covered with canvas and painted, tarred, or otherwise protected from decay through damp or by atmospheric corrosion.