. Bulletin of the Department of Agriculture. Agriculture; Agriculture. LOGGING IN THE DOUGLAS FIR REGION. 75 them are frequently far beyond their normal capacity. To see them hauling logs larger than 10 feet in diameter and 24 feet in length over rough ground on a "straight" line is to marvel that they are not wrecked in a short time. That they are not is due to the fact that they are simply, compactly, and pov^erfully built of the best adapted material. The frame or bed of the machine, on which the security of all fastenings and the permanency of alignments of all Avorking part
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. LOGGING IN THE DOUGLAS FIR REGION. 75 them are frequently far beyond their normal capacity. To see them hauling logs larger than 10 feet in diameter and 24 feet in length over rough ground on a "straight" line is to marvel that they are not wrecked in a short time. That they are not is due to the fact that they are simply, compactly, and pov^erfully built of the best adapted material. The frame or bed of the machine, on which the security of all fastenings and the permanency of alignments of all Avorking parts depend, is strong and rigid, being made of the heaviest standard section of steel beams spaced by heavy crossbars of cast iron or Fig. 30.—Compound-geared yarding engine. Logging engines are equipped with high-pressure boilers of the vertical type, built of 60,000-pound flange steel. They have a work- ing pressure of from 150 to 200 pounds (generally 200 pounds), and are guaranteed to pass Hartford inspection. They range in size from 48 inches in diameter and 96 inches in height to SO inches in diameter and 153 inches The extreme height and high working pressure of these boilers, the limits of which have been reached, is the result of constant increase in the cylinder sizes. The width of the engine frame, by limiting the diameter of the boiler, has restricted the dimensions of the round fire box, resulting in too small a proportion of grate to heating sur- face. To overcome the steaming difficulties resulting from insuffi-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Dept. of Agriculture. [Washington, D. C. ?] : The Dept. : Supt. of Docs. , G. P. O.
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