526
HISTORY OF ENGINEERING.
Hook I.
were rejected; they were often formed along steep hill-sides and rocky precipices, and arealways sufficiently wide to admit of two carts passing. Wherever the land-owners requireda road, an application was made to the parliamentary commissioners, accompanied by theoffer of defraying half the expenses ; the district was then surveyed, and the cost estimated,after which the memorialists were called upon to deposit half the amount in the Bank ofScotland ; detailed working drawings and specifications were prepared, and the groundmarked out, and contractors were found to undertake the work under proper surveyors.Where the length of road did not exceed ten miles, it was generally contracted for by oneperson, but it was frequently divided among many, separate tenders being given for dif-ferent lots. The general superintendent and special inspector were appointed by the chiefengineer, Mr. Telford, to whom the inspector made a regular monthly statement, whichwas afterwards sent to the commissioners.
When the roads were completed, those who contributed the moiety of the expense wereinvited to survey them, and to join in the certificate that the whole was executed agreeablyto the contract and specification, after which the last eighth of the total sum retained waspaid to the contractors.
There were 920 miles of new road, and 1117 bridges, built in the course of 18 years,under 120 contracts, witnout recourse being had to a court of law in any one instance.
Many of these roads were originally mere tracks, and it was sometimes necessary to carrythe lime for making the mortar in sacks on the backs of horses for upwards of twentymiles. The stones for the arches of the bridges were brought by sea, many districts notaffording sufficient to cover a drain 2 feet in width.
The setting out these roads, and constructing the bridges throughout the most unfre-quented parts of Scotland , called into practice a new class of engineers, hitherto unknown,who soon systematised the labours they had to perform, and introduced a nomenclatureand method by which others could direct similar operations. An evident improvementtook place on all our mail-coach roads, which was imitated by those who had the charge ofother trusts. Material was sought for where it could be most easily obtained, and ex-periments were tried upon its quality before contracts were entered into for its employ-ment ; many surveyors, who were before incompetent to judge of the quality of the metalwith which they formed the crust of a road, turned their attention to its chemical and me-chanical properties. Small, smooth, round pebbles were no longer heaped together to bespread over the middle of the carriage-way, but limestone or granite broken into angularmasses was carefully laid over the whole to one uniform depth. Every precaution w;istaken for draining and keeping the road clean ; the manner in which these operationswere carried out cannot be better understood than by referring to the following instructionsdrawn up by Mr. Telford, which may be serviceable to those who have similar works toperform, and as there is now every probability of railroads becoming general, it is peculiarlynecessary to preserve documents which relate to so direct an evidence of our progress incivilisation. •
“ General specification for the Highland Roads —The road to be formed to the full breadthof 20 feet in the clear, including the side drain and green margin, except on places wherethere is an absolute necessity for cutting the whole breadth of the road in solid rock; andin those places the breadth of the road shall be 18 in the clear, between the parapets whichmay be necessary for a safeguard, and those parapets are to be 2 feet in thickness at thebottom, so that in rock the cutting will be 20 feet in breadth, and in all cases the road is tohe so laid out, that there shall be nr) quick bendings, nor its upper side interrupted by pointsof rock.
“ On dry bottomed ground, gravel of a proper quality, out of which all stones, above thesize of a hen’s egg, shall have been previously taken, shall be laid to the depth of 14 inchesin the middle, and 9 inches at the sides ; but the stones which are taken out of the gravel,and do not exceed 4 inches in size, may be laid for that thickness below the gravel, and inthat case 10 inches only of cleansed gravel will be required.
“ On mossy ground or swampy soils, if the moss or soft matter is not more than 2 feet inthickness, and a hard bottom below this moss or soft matter, it is to be wholly removed,
and the road formed on the harder substance as above described; but when the moss orsoft matter is more than 2 feet in depth, the contractors are to have their option of eitherremoving it, or forming the road upon the top of it in the following manner.
“ Where the surface is level, and covered with sound sward or heath, there must be laidtwo rows of swarded turf, with the swarded side of the one downwards, and of the other