'552 PRACTICE OF AGRICULTURE. Part III. 



be found in countries that are not absolutely mountainous, but where the ground regu- 

 larly declines towards the vales or large rivers." 



3536. A rough section of the proposed line will enable the engineer to see the places of 

 the heights and breadths of the various summits, or ranges of high land that are to be 

 passed, and whether any two or more adjacent ones can be connected by a long summit 

 level, without deserting any considerable town or point of trade, which will diminish the 

 difficulties of supplying the canal with water, as every such junction of summits preserves 

 the water of two lockages, beside presenting so many more points at which the canal can 

 be supplied with water, from springs and rivulets above its level, or where, in less favor- 

 able situations, the same can be collected in a lower level to be pumped up. From one 

 end of the proposed summit level it will be right now to proceed with the survey, tracing 

 the level accurately and marking the same by pegs or stakes, that will last for some time, 

 and be known by the surveyor, who is to follow and make a plan of the line ; the levels 

 being frequently transferred to what are called bench marks, upon the trunk of a tree, a 

 large post, or a building,. the same being noted so particularly in the field or survey book, 

 that they may be readily found for years afterwards. We suppose the engineers, by this 

 time, to have settled the rise that each lock should have, according to the dimensions 

 adopted for the canal, the probable supply of water on the summit, and other circum- 

 stances ; the summit level will be traced as above, till the proper place occurs for making 

 a fall of two or more locks, at about 100 yards, or a little more from each other; and the 

 places of these falls being marked, the level is again to be pursued and traced from the 

 bottom of them, and marked out as before, till the opportunity occurs for another pair or 

 more of locks, or till some obstacle, as a gentleman's park, houses, gardens, orchards, 

 mills, roads, &c. present themselves at a distance ; when it will be proper, after transfer- 

 ring the level arrived at to a proper and permanent mark, to proceed forwards, and to ex- 

 amine and well consider the different ways and levels, if more than one of such present 

 themselves, by which the obstacle can be passed. From the most confined part of the 

 course for the canal, owing to the obstacle, it will be right to level back, till the former 

 work is met, and to determine the most eligible mode of bringing the two levels together, 

 upon the principles before stated ; if they can be applied, either by adding another lock, 

 or taking one from any of the sets of them which had been before marked out, as occa- 

 sion may require, and marking out the new levels thereby occasioned : the line between 

 the summit and the first obstacle, or confined part of the course, being thus adjusted, a 

 new point of departure is to be taken from such obstacle, and the level pursued as before, 

 till the fall for a pair or more locks can be gained, at the proper distance from each other. 

 In this way, the patience, perseverance, and abilities of the engineer must be exercised, 

 until a practicable line of some length is obtained, and staked out ; when the assistant 

 land-surveyor must follow, and make a correct and particular plan of the line of the 

 several proposed locks, embankments, tunnels, &c. upon the same, and of the several 

 fields, or pieces of land through which it passes, or that come within 100 or 150 yards of 

 it in any part : it will likewise be the business of the surveyor to ascertain, with the ut- 

 most care, the boundary of every parish and township, what county each is in, the proper 

 names of the owners and occupiers of every piece of land in each, however small, upon or 

 within that distance of the line, with reference to the same upon his plan ; and to describe 

 correctly all public and private roads and paths that cross or intersect the line, and to and 

 from what places they lead ; the course of all brooks or streams of water, and particular- 

 ly such as lead to and contribute to the supply of any mill : the situation of the houses 

 and towns upon the line, or within some miles of it, should also be determined ; the 

 nearer they are the greater accuracy will be necessary. A complete plan of the line, and 

 all the projected collateral cuts, feeders, reservoirs, &c. being finished, the engineer will 

 enter on a most careful revisal of the whole scheme, with this plan in his hand ; on which 

 all the places where culverts or drains will l)e required, are to be marked, as also the pro- 

 per places for the bridges, and the necessary alterations of the roads and paths, which will 

 be cut oflTby the canal, so that the public will not be inconvenienced and turned long 

 distances round about, and still, that as few bridges as possible, and those in the least ex- 

 pensive places, may be erected. In some instances new channels will require to be cut 

 for brooks and water-courses, to a considerable extent, in order to save culverts, or bring 

 them to the most desirable spots. For proper security against accidental errors, the 

 whole of the levelling should now be gone over again, and the several bench marks com- 

 pared, and renewed with the utmost care by the engineer's assistants, while he is pro- 

 ceeding with the necessary inquiries and calculations, for an estimate of the whole expense 

 of the undertaking. 



3537. The supplying of a canal with ivater, in a great number of instances, occasions 

 no inconsiderable share of the whole expense, either in the first cost of mills or streams 

 of water, in land for, and labor in, constructing reservoirs, engines to pump water, &c. ; 

 or annually ever afterwards, in the fuel for. and repairing of engines, hire of water from 

 mills in dry seasons, &c. j this subject should, therefore, employ the most sedulous attcn- 



