. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. MR. DENTON'S "A" LEVEL. The annexed woodcut shows the instrument —its figure will explain the rea- son of its being called the " A Level;" while the observer will compre- hend at a glance its portability and the facility with which it may be used either on the surfar^e or in the trench. The b ir B turning up on a hinge and falling into grooves cut in the legs A, these legs may be closed, as a pair of compasses fold ; and the whole may be used as a rod for
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. MR. DENTON'S "A" LEVEL. The annexed woodcut shows the instrument —its figure will explain the rea- son of its being called the " A Level;" while the observer will compre- hend at a glance its portability and the facility with which it may be used either on the surfar^e or in the trench. The b ir B turning up on a hinge and falling into grooves cut in the legs A, these legs may be closed, as a pair of compasses fold ; and the whole may be used as a rod for measurement. The legs A are sufficiently narrow to stand in the narrowest trencli; while the false feet F aftord the means of stationing the instrument on the surface. The object of the instrument is to assist foremen and workmen in testing and preserving an uniform fall in all works requiring such regu- larity. A spirit level, if understood by workmen, is a thing easily put out of order, and is at all limes liable to be broken; its use, there- lore, is dreaded by workmen, as a process involving too much time, rare, and precision, for their fingers to perform. In drainii'g and sewering, if the first object of the operator is lo direct his drains according to the best fall of the ground, the next point of importance is that the floor of the trench, and the course of the tiles, soles, or bricks should be even and regular from the top to the bottom of the drain. Any hollow in the drain intercepts the sedi- mentary matter which the How of the drain water would otherwise cairy out with it; the sectional area of the water-way is thereby les- sened, and llie sediment, gradually accumulating, after a time causes a stoppage, the drain bursts, and the work has to be re-done. 'J'iie levrl placed in the trench, as it is dug preparatory to laying in the tiles, ludirales by the plumb-line any irregularity bad work may occasion. Such use of the instrument is merely analogous to the mode by
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