File:A manual of the principles and practice of road-making- comprising the location, consruction, and improvement of roads (common, macadam, paved, plank, etc.) and rail-roads (1853) (14779033803).jpg

Identifier: manualofprincipl00gill (find matches)
Title: A manual of the principles and practice of road-making: comprising the location, consruction, and improvement of roads (common, macadam, paved, plank, etc.) and rail-roads
Year: 1853 (1850s)
Authors: Gillespie, W. M. (William Mitchell), 1816-1868
Subjects: Roads Railroads
Publisher: New York, A. S. Barnes & Co.
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Northeastern University, Snell Library

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drives, such asthose laid out by landscape gardeners in parks, cemeteries,&c., curvature is the rule, and straightness only the ex-ception. In them the object is to wind as much as possible,m Hogarths line of grace, so as to obtain the greatestdevelopment of length which the area of the ground willpermit, but at the same time never to appear to turn forthe mere sake of curving. Some reason for the windingsm.ust always be suggested, such as a clump of trees, a riseof ground, a good point of view, or any object which mayconceal the artifice employed. The visiter must be de-ceived into the belief that he is traveUing over a large area,while he is truly only retracing his steps and constantlydoubling upon his track ; but he must do it unconsciously,or at least without knowing the precise manner in whichthe pleasant deception is efiected. Ars est celare artem. The map on the opposite page, representing the roadsand paths in Greenwood Cemetery, will somewhat illus-trate this principle.
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32 WHAT ROADS OUGHT TO BE. 2. WHAT ROADS OUGHT TO BE AS TO THEIR SLOPES.LOSS OF POWER ON INCLINATIONS. Every road should be perfectly level. If it be not, alarge portion of the strength of the horses which travel itwill be expended in raising the load up the ascent. Whena weight is drawn up an inclined plane, the resistance ofthe force of gravity, or the weight to be overcome, is sucha part of the whole weight, as the height of the plane is ofits length If, then, a road rises one foot in every twentyof its length, a horse drawing up it a load of one ton iscompelled to actually lift up one-twentieth of the wholeweight, i. e., one hundred pounds, through the wholeheight of the ascent, besides overcoming the friction ofthe entire load. Fig. 2. Let DE re-present the in-clined surfaceof a road uponwhich rests awagon, the cen-tre of gravity ofwhich is sup-posed to be at C. Draw CA perpendicular to the horizon, and CB perpen-dicular to the surface of the hill. Let CA represent the forceof gr

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