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15' 16' 17

Direct-Indirect Radiators.

holds chiefly for want of a better. The main difficulty lies in the great difference in the value of the various kinds of surfaces, no distinction being made in such rating between plain, extension or veiled surface. The variation is enhanced also by the fact that radiators are to a large extent overrated, especially in the less common sizes and styles; and owing to the difficulty of accurately measuring the surface, this fact is very generally overlooked. A number of methods have been proposed and tried for measuring the surface of radiators which are made in ornamental design and with all kinds of irregular surfaces. In the course of a large experience with radiators of all kinds, the author tried many different methods and finally devised one which he has found comparatively simple and very reliable. By this method all irregular surfaced are measured by covering them with very thin flexible paper which must be carefully turned and folded into all irregularities of the surface. After being thus fitted, the paper should be rubbed by blackened fingers. They are generally sufficiently soiled for the purpose from handling the radiators. In this way when the paper is spread out, the part that was folded under can be readily distinguished, and the actual area of the surface can be determined by measuring the blackened parts with a planimeter. In lieu of a planimeter, thin cross-section paper can be used and the areas determined by counting the small squares. In measuring up a radiator loop, it is best to divide the surface by thin lines of white chalk or paint and measure each division separately. The parts