Drawing Instruments. A complete set of drawing instruments comprises a very considerable number of pieces, - several, however, being duplicates, so far as the principle of their construction and the mode of using them is concerned, but of different sizes and forms; - but a very wide range of work can be done by the aid of the following: - (1.) The " large compasses," with shifting leg, into which can be put (a) a leg carrying a pencil, and (b) a leg carrying a pen, for the drawing of pencilled and inked circles and parts of circles. (2.) The "spring compasses," one leg of which is adjustible by means of a spring acted upon by a small set screw. By this instrument, when a measurement is taken in the compasses - as in dividing a line into any number of equal parts - if the measurement is either a trifle too long or too short, the accurate measurement may be taken by adjusting the screw. (3.) "Spring dividers" - these are small compasses for taking small measurements, the legs of which are connected by a spring and a screwed link, the latter being provided with a small set screw, so that an accurate adjustment of the divider is easily attainable; and, when once set, the measurement taken will be retained, as the screw and spring keep the legs always at the same distance. This convenience is very great when the same measurement is to be often repeated in making the drawing. (4.) The " pencil bow compasses," for describing small circles and parts of circles in pencil. (5.) The "ink bow compasses," for describing small circles and parts of circles in ink. (6.) The "drawing pen." The above named instruments will not be here further described. Without them the pupil cannot even begin to the work of drawing, he must, therefore, purchase them; and a few minutes' examination of them will convey to him a more satisfactory notion of their peculiarities and uses than pages of description here. Fuller remarks upon them will, however, be found in the work on Technical Drawing, page 6. To the above will be required a common (7.) foot-rule.