Naked pipe 100. Two layers asbestos pipe, 1 inch hair felt, canvas cover 15.2 The same, wrapped with manila paper 15. Two layers asbestos paper, 1 inch hair felt 17. Hair felt sectional covering, asbestos lined 18.6 One thickness asbestos board 59.4 Four thicknesses asbestos paper 50.3 Two layers asbestos paper 77.7 Wool felt, asbestos lined 23.1 Wool felt with air spaces, asbestos lined 19.7 Wool felt, plaster paris lined 25.9 Asbestos molded, mixed with plaster paris 31.8 Asbestos felted, pure long fibre 20.1 Asbestos and sponge 18.8 Asbestos and wool felt 20.8 Magnesia, molded, applied in plastic condition 22.4 Magnesia, sectional 18.8 Mineral wool, sectional 19.3 Rock wool, fibrous 20.3 Rock wool, felted 20.9 Fossil meal, molded, 3/4 inch thick 29.7 In general the thickness of the coverings tested was one inch. Some tests were made with coverings of different thicknesses, from which it would appear that the gain in insulating power obtained by increasing the thickness is very slight compared with the increase in cost.[19] [19] Rolla C. Carpenter, “Heating and Ventilating Buildings,” p. 229. New York, John Wiley & Sons, 1905. Some properties of matter seem to have family ties. Tenacity and conductivity for heat, as an example, go together; all the tenacious metals as a group are conducting as well. Conversely, the non-conductors,--felt, gypsum, and the rest, are structurally weak. If the inventor could lay hands on a material able to withstand high pressure and, at the same time, carry off wastefully but little heat, he would build with it cylinders for steam engines much more economical than those of to-day He would also give cooking apparatus of all kinds a covering which would conduce to the health and comfort of the cook, while, at the same time, heat would be economized to the utmost. One of the advantages of electric heat is that it can be readily introduced into kettles and chafing dishes surrounded by excellent non-conductors; the result is an efficiency of about ninety-five per cent., quite unapproached in the operations of a common stove or range. Norwegian Cooking Box.