The deflection is indicated by a pointer upon a graduated scale, the readings being interpreted by comparison with two standard specimens supplied with the instrument.
The end knife-edges are adjusted and tightly jammed into exact position by means of wedge pieces and set screws, and the beam is furnished with delicate adjusting weights at its top. The position of the beam with respect to the horizontal is shown by a horizontal pointer (not shown) projecting from one end of it, which plays past a scale, each division of which corresponds to the i l oth or i hth of a grain according to the size and delicacy of the machine.
However often she told herself that she must not get irritable when teaching her nephew, almost every time that, pointer in hand, she sat down to show him the French alphabet, she so longed to pour her own knowledge quickly and easily into the child--who was already afraid that Auntie might at any moment get angry--that at his slightest inattention she trembled, became flustered and heated, raised her voice, and sometimes pulled him by the arm and put him in the corner.
The diamond-shaped pointer is always in focus; focusing for individual eyesight is effected by turning the eye-piece, which is furnished with a scale for readjustment.
The weight of the goods is recorded by means of an index pointer fixed to the casing on one side of the vertical slot, and the money values are opposite the figures defining the rates per lb, which are marked on the edge of the casing below the hori zontal slot.
The weighing is conducted in the usual way by vibrations, except when the weight be small; it is then advisable to bring the pointer to zero, an operation rendered necessary by the damping due to the adhesion of water to the fibre.
Minor improvements in tangent sights certainly were made, notably an automatic clamp, but quadrant elevation was mainly used, and in the case of guns equipped with position-finders (see Range-Finder) the guns could be layed for direction by means, of a graduated arc on the emplacement and a pointer on the mounting.
To take a reading the torsion-head is turned until an aluminium pointer attached to the coil is brought to the zero position on a small scale; the strength of the field is then proportional to the angular torsion.
Personal error is to a great extent eliminated, power of vision extended, the sight is self-contained, there is no fore-sight, a fine pointer in the telescope being aligned on the target.
We may infer that the limits of efficiency in the two methods are the same when the length of the pointer is equal to the width of the mirror.