An adjustable standard of measure employed in various arts where a number of articles of the same kind are required to be as nearly as possible of the same dimensions. Gauges are various, constructed according to the purposes to which they are to be applied. The cut on the following page represents a gauge contrived by Mr. H. R. Palmer, for the purpose of making a line along the centre of any parallel or tapering solid. It answers all the purposes of a common carpenter's gauge, whilst it is peculiarly serviceable in other respects, for which the common gauge is wholly inapplicable; in making mortices, and enabling workmen to measure from a centre line, and to work with greater accuracy and facility; and in many other cases it will be found a very convenient instrument, a is a square bar of hard wood, having two sliding cheeks b d fitted tightly to it; the cheek b is fixed fast on one end of the bar, whilst the other slides upon it, but it may be made fast at any required place by means of the thumb screw c; at the end b a common scribing point is fixed in the bar, and with this and the sliding piece d it forms the common gauge used for drawing parallel lines from the edge of any piece of wood work.
The addition made by Mr. Palmer consists of the two brass arms f and g, of equal lengths, and which are centered in the two sliding cheeks at a a; the other ends arc jointed, together by the screw h, which is formed into a sharp conical point beneath to mark the work with. In using this gauge it is evident that the point of the screw h will always keep in the centre between the two cheeks b d. If the work is not parallel in its width, then the screw c must be loosened, and the two cheeks b d must be kept pressed towards each other, so as to be in contact with the sides of the work, when the point g will traverse along the centre of the piece as correctly as if the sides were parallel, because in all situations it preserves an equal distance from the two cheeks b and d; these cheeks have grooves made in them to receive the brass arms f and g when the cheeks are brought into contact.