121 



DRAWING INSTRUMENTS. 



Drawing 

 Instru- 

 ments. 



Case of In- 



stninioUs. 



Pen. 



Pencil. 



Compasses. 



Drawing 

 compasses. 



Pen-leg. 



Pencil- leg. 

 Dotting- 



Bow-corn- 



ttttor. 



Frotractor. 





Ptedh, 



DRAWING instruments may be divided into several 

 kinds : First, Those for drawing lines, as pens, pencils, 

 crayons, and steel pens. Id, Instruments for guiding 

 or directing the above, as rulers for drawing straight 

 or slightly curved lines, compasses for drawing circles, 

 the elliptograph for drawing ellipses, and the geometrical 

 pen for producing a great variety of curves. 3d, Those 

 which are used for marking or setting out distances, or 

 dividing them, as compasses and divided scales, sectors 

 and protractors; also instruments for dividing circles 

 and ellipses. 



It is customary with artists, whose operations are 

 connected with mathematical designing, to provide 

 themselves with a selection of drawing instruments, 

 containing such as they find, by experience, are most 

 frequently wanted, and best adapted to their particu- 

 lar purposes. What is called a complete case of mathe- 

 matical drawing instruments, such, as may be obtained 

 at almost any shop, contains the following articles : A 

 steel drawing-pen, the handle of which unscrews, and 

 has within it a sharp steel point, for the purpose of 

 pricking centre points. A black-lead pencil, with a 

 silver ferrule or top formed to the shape of the point 

 of a knife, but made with a smooth blunt edge, for the 

 purpose of scratching or tracing lines upon the paper : 

 these lines are permanent, though not visible without 

 particular examination. A p;iir of compasses for mea- 

 suring distances. Another pair of compasses, of a 

 larger size, for the same purpose, and also for drawing 

 circles ; to effect this, one of the legs is fitted in a socket, 

 and fastened by a screw, to admit of removal for the 

 purpose of applying other legs to it: these are, a steel 

 pen leg, for the purjxise of drawing circles in ink ; a 

 leg adapted to hold a piece of black-lead pencil, for de- 

 scribing circles in pencil; also a dotting leg, which is a 

 small wheel, with several point?, something resembling 

 the rowel of a spur : it is fitted to revolve between two 

 blades, like those of a steel pen, and these are, in the same 

 manner, formed out of the leg, which adapts to the com- 

 passes. The space between the blades being filled 

 with Indian ink, and the wheel rolled upon the paper 

 while the compasses turn round, its points make equi- 

 distant dots in the circle which the compasses describe; 

 and as the points of the wheel pass through the drop 

 of ink which is held between the upper part of the 

 two blades of the instrument, they are successively re- 

 plenished witli ink. A small pair of bow-pen com- 

 passes : these are small compasses, with a pen leg per- 

 manently attached to them, so that it cannot be remo- 

 ved : they are useful to draw very minute circles. A 

 sector, which is a scale containing many lines of ma- 

 thematical divisions, which are very extensively useful 

 Cor trigonometrical operations. A parallel ruler, for 

 drawing straight lines parallel to eacli other. A plain 

 scale, which has lines upon it graduated with equal di- 

 visions, of different values. Al-o a protractor, or semi- 

 circle, divided into degrees, for laying down angles. 

 All these instruments are so well known, that it is 

 needless to give a more minute explanation of them, 

 particularly as those which are sold in such kind of 

 ease* are not made on the btst construction, having 

 many detects, which it has been the study of several 

 artists to remedy. 



In our observations on instruments, we shall begin 

 with those which are employed for drawing lines ; and 



VOL. VIII. PART I. 



Drawiug 



Instm- 

 ments. 



of these, black-lead pencils come first to be mentioned. 



They should be of very pure lead, without any mix- 



ture of hard particles. The hardness of its substance 



should be adapted to the purpose for which they are to , , .""""" 



be used : for mathematical drawing, the lead should be p cnc iis. 



hard, so that it will cut to a fine point, and preserve it 



sharp for a considerable time without sharping, and at 



the same time it should mark with so little pressure, that 



it will not penetrate or indent the paper. The mark it 



makes should be quite superficial, that it may be total- 



ly obliterated by a light application of the Indian rub- 



ber. This is a very essential requisite in a pencil ; for 



if the paper requires much rubbing to clean off the 



pencil marks, its surface will be injured, and prevent 



any good finishing or colouring upon it. 



Some pencils are made by reducing the black lead to 

 powder, and recomposing it by the admixture of some 

 glutinous substance. By this means they separate the 

 impurities from the lead, and make tolerable pencils ; 

 but these do not stand to so good a point as others 

 made from solid lead, when the same is of the best qua- 

 lity. Messrs Brookman and Langdon of London, (28, 

 Russel Street, Bloomsbury,) have invented a process, 

 by which they purify the lead, and produce pencils of 

 any required quality. With respect to the hardness, 

 these makers distinguish them by the following marks : 

 HH, very hard, for engineer or shipbuilders' use ; H, 

 rather less hard, for architects, who require less accu- 

 racy, but more freedom for sketching in ornamental 

 parts; F, fine drawing pencils, are of a middle degree of 

 hardness these are not intended for ruling lines, but for 

 drawing figures, landscapes, &c.; B, black for shading, 

 are rather soft lead ; BB, extr.i black for deep shadow- 

 ing ; and BBB, are prepared as black as possible for 

 shadows. All these marks are of a very superior kind, 

 having the requisites we have enumerated for good 

 pencils, particularly the HH, which stand to a point 

 so long, that cutting the pencil with a knife two or 

 three times in the course ot a day's work will be suffi- 

 cient. The point will frequently wear so as to draw 

 rather a broad line ; but it is better to restore the point 

 by rubbing it on a piece of paper, and at the same 

 time turning it round, than to attempt cutting it every 

 time with the knife. For this purpose, a piece of the 

 very finest glass, or emery paper, is very useful. The 

 point so formed should not be too acute, or it may 

 break. 



Steel pens, for drawing lines in ink, are made in ma- g j 

 ny different forms ; but they all consist of two blades 

 of steel, so fitted together that they have a tendency 

 to spring open from eacli other. They have a screw, or 

 equivalent contrivance, by which the points can be 

 closed together to any required degree, leaving a small 

 opening between their points, through which the ink 

 flows down from the upper part, where a drop of it is 

 retained. When the pen is used, it must be fairly ap- 

 plied to the edge of the ruler, and drawn along it, ta- 

 king care to hold it so that both points touch the paper 

 at once, or it will not draw an even line. It will act 

 best if it is rather held in an, inclined position, in the 

 direction of its motion ; it then leaves upon the paper a 

 breadth of ink equal to the opening between the points, 

 and this may at pleasure be increased or diminished. 

 The points of the pen should be rather round, that they 

 may not penetrate the paper; but in the thickness, 

 Q 



