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ABCD the drawing board, EFGH the drawing paper, 
TT Stanley’s ebony-edged T-square, resting against the 
pins KE, during the operation ; MM Stanley’s ebony- 
edged set-square, which slides along the edge of TT ; 
SS Stanley’s engine-divided, millimetre scale, connected at 
one end to the edge of the set-square M, by pins and elastic 
string NN, so as to slide with the set-square, and have its 
graduated edge parallel to the edge of TT, and also parallel 
to the lines KK, K'K' on which the scales have to be con- 
structed ; LL a very fine ink line at right angles to the edge 
of the scale, beyond the extremity of the required scale KK, 
on the right hand side, to which the divisions of the milli- 
metre scale are adjusted by the eye, with the aid of a lens 
placed on a stand, its axis in a vertical plane through the 
line LL ; a fine adjustment of the line and division is 
obtained by means of the blunt handle of the drawing pin, 
used as a lever against the end of the scale, the surface of 
the board or the paper being the fulcrum. 
The divisions of the map scale are drawn at Z,Z, with a 
very thin drawing pen, very close to the edge of the set 
square, so that the variation of the inclination of the draw- 
ing pen is a very inappreciable error. If the map scale is 
required to be longer than the scale S, another very fine 
perpendicular ink line L'L' must be drawn at an exact * 
multiple of 10 millimetres distant. 
To prevent mistakes in drawing the principal divisions, 
the line LL is arranged so that they may be drawn when 
the corresponding principal divisions on the scale SS are 
coincident with the line. 
The advantages of this method of drawing a map scale, 
arise from the fact that the error due to the observation of 
the coincidence of two lines, is much less than that of plot- 
ting a point opposite each division of the millimetre scale. 
Also in the fact that the error due to drawing a line 
with a thin pen very close to the edge of the set-square. 
