[1] For this purpose the following publication will be found useful: Farmers' Bulletin 1889, Fireplaces and Chimneys.
The heatilator is a built-in recirculating steel unit consisting of metal sides and back to form a heating chamber, adjacent to the fire pit, which draws cold air through a register at each side near the floor and after the air is heated ejects it through similar registers above. It should be installed in conformity with the manufacturer’s directions, taking care to select a stock-size unit suitable for the dimensions of the fireplace opening and to erect the surrounding masonry accordingly.
After all the openings have been properly calked and the logs brushed clean, it is often desirable, although not absolutely necessary, to treat the log surfaces with some sort of preservative material. Logwood oil is excellent for the exterior. The colorless variety is preferable in most cases but, if some color is desired, add just enough burnt umber, or raw sienna paste, to give the proper shade. For interior finish, apply a coat of clear shellac and then one or two coats of dull varnish. The trim can be treated in a similar manner to preserve the pleasing effect produced by the natural surface and color of the wood.
Examples of modern log construction are shown in figures [32], [33], and [34]. Early types of log structures are illustrated in [figure 35].