SURVEYED BY I. T. W. BELL 1860A. Reid’s Lithog. 117 Pilgrim St. Newcastle.
Plan of
AN ANCIENT WATER COURSE EXTENDING FROM
SAUGHY BIG WASH POOL TO ÆSICA GREAT-CHESTERS.

ETYMOLOGY OF ÆSICA.

Celtic authorities all agree in tracing the name Æsica to a word signifying water. The propriety of such an appellation does not at first sight appear. The camp is far from either the eastern or western sea; no lake is visible from its ramparts; the only water which is near is the Haltwhistle-burn, a somewhat tiny stream. The low ground to the south has a fenny aspect, but the station itself stands high and dry, though upon a part of the mural ridge less elevated than usual. It is not improbable that it may have derived its name from an aqueduct which leads the water from the Greenlee-lough to the camp. As this water-course has hitherto escaped the notice of writers upon the Wall, and is a work of considerable interest, a somewhat detailed description of it may be allowable.

THE WATER-COURSE AT ÆSICA.

The camp, though not greatly elevated, stands higher than the ground, either north or south of it. The country to the north, though generally flat, is studded with numerous hills of moderate elevation. On the sides of some of these, about two-thirds up, may be noticed a line that reminds the spectator of the parallel roads in Glenroy and other places. On examination, it is found to be an artificial cutting, made with evident reference to the maintenance of the water level. The sections given in [Plate XVI]., shew its size and form. In some places the water stands in it yet; in others a mass of peat fills it; and very frequently, where the channel has been obliterated, its course is shewn by a line of rushes, which grow on the damp ground. Wherever the water-course can be distinctly discerned, it has been laid down in the accompanying plan by a green line; where the traces of it are lost, the line of the water level has been pursued, and is indicated by dots of the same colour.

THE WATER-COURSE.

The whole length of the water-course is six miles; the distance in a straight line is little more than two miles and a quarter. It takes its commencement at the Saughy-rig-washpool, which is formed by the occasional damming up of the Caw-burn, at about a mile from its exit from the Greenlee-lough. In the immediate vicinity of the burn, the side of the water-course next the rivulet which would be endangered by the overflowing of the natural stream, is made up with flat stones put in endwise, some of which still remain as shewn in the section at B, in the plan. In its course to the station, in order at once to preserve the level, and avoid the necessity of using forced embankments or stone aqueducts, it is taken along the sides of the moderately elevated hills which rise from the plain. So ingeniously is this done, that once only has it been necessary to cross a valley by an artificial mound of earth. This has been at a spot between the third and fourth mile of the water-course, and which is still known in the district by the name of Benks-bridge, though probably few of the inhabitants are aware of the evident origin of the term. Some ingenuity has been employed in fixing the site of this mound. It is placed in that part of the valley where there is a slight descent on each side of it; the drainage of the surface is thus provided for without the use of a culvert; the surface water on the west, naturally making for the Halt-whistle-burn, that on the east for the river Tipalt. The mound which has taken the water-course across the valley at Benks-bridge has entirely disappeared, having probably been absorbed, in the course of ages, by the mossy ground on which it stood. The whole fall of the water-course, reckoning from the Wash-pool to the bottom of the arched chamber in the centre of the station is thirty feet. This is distributed over its entire length in the way shewn in the following table:—

ft.in.m.f.c.ft.in.
Commencing atA00At 260½1110fall
m.f.c.275E144”
006B210fall.300216”
015310”303237”
02437”306235”
034½37”3132910”
04936”335253”
06037”350North end, Benks-bridge.254”
078½40”350South end, Do.297”
106½41½”415299”
113½37”4582911”
132½36”535½286”
140C310”5442811”
20559”555290”
216½114”600Present bottom of arched chamber in centre of station.304”
229½D112”

The nature of the ground threw considerable difficulties in the way of the engineer, which accounts for the exceedingly tortuous nature of the track pursued. It is indeed remarkable that without the aid of accurate levelling instruments, any one could be so fully assured that the requisite fall existed as to venture upon the task of its formation. The workmen in the execution of the design probably drew the water along with them as they proceeded. In one place, (G) they seem to have made too free with the fall, and after proceeding for some distance, (upwards of a furlong) have retraced their steps, and constructed the cutting at a higher level. In crossing the valleys, there is sometimes an unusual loss of fall. This is particularly the case at the third mile (E) where there is a difference in the level of the course, on the opposite side of the slack, of nearly ten feet. This valley is permeated by a streamlet, and to take the water across it at the level previously preserved, a stone aqueduct would have been necessary. Appearances seem to indicate that an easier plan was adopted. A dam being formed across the hanging side of the valley, the water of the course was allowed to deliver itself freely into it, and eventually rising after the manner of a mill-head to the level of the course on the western side, pursued its way as before. That this plan was the result of a change in the design of the architect seems evident, for on the eastern side of the valley a second cutting (E) has been made at a lower level than the other, apparently with the view of leading the water more gradually to the lower point.

Unfortunately all traces of the water-course are lost for some distance before approaching the station, so that it cannot be ascertained where it entered it, if it did so at all.