By this term is commonly understood the mechanical drawing-pens, consisting of a pair of delicately-formed steel blades, the ends of which are drawn together and adjusted by means of a fine set-screw; these pens are mounted with handles of various materials, but those of ivory or ebony are deservedly preferred. These instruments are manufactured by Mr. Elliott, of High Holborn, in the highest perfection. The extremities of the steel blades which form the pen should be very narrow ellipses, and should perfectly meet, without the minutest projection of one piece over the other. The outside of the elliptical end should be rubbed on a hone until it is as thin as the edge of a knife: in this state the points would cut the paper; but the sharpness must be taken off by gently drawing them over the stone upon their edges, and finishing them upon a soft polishing-stone. A smoothness is thus given to their edges, which makes them glide over the paper, although they will still be left so thin that their edges can scarcely be discerned.
By this management, lines may be drawn while the points of the pen are at a distance from each other, not perceptibly exceeding the breadth of the lines produced, which is of consequence, not only to the equable flow of so viscid a fluid as Indian ink, but to obtaining a well-defined stroke.
A drawing-pen was lately presented to the Society of Arts, by Mr. Bryan Donkin, which he had brought from France. It is calculated to make lines of only one uniform thickness: the cavity which contains the ink being enclosed all round, keeps it free from dust, and prevents it from drying, and clogging the drawing-point so quickly as those of the ordinary construction. Fig. 1 (in the following page) shows the pen, with the handle broken off; a and b are the two limbs, jointed at c, and held close by the sliding ring d; the dotted line3 represent the upper portion a as opened, to receive the ink, with the ring d slidden back beyond the joint. Tig. 2 shows the underside of the limb a, in a separate state; at c is the hole to receive the centre-pin; e is the cavity for the ink; g g, notches for receiving two projecting pieces, as shown at f in Fig. 1.
An extremely simple and ingenious mode of making a drawing-pen of the last-mentioned kind (that is, to make a line of only one thickness,) was invented by Mr. Robert Christie; and having made several according to his instructions, which answer very well for tracing, as it moves with equal facility in any direction, we insert a notice of it in this place. The annexed cut represents one of these pens, in a neatly-turned handle; but we made them at the solid end of black-lead pencils, for the convenience of readily using either lead or ink. The process, as directed by Mr. Christie, is as follows: - A piece of sealing-wax, about the size of a marrowfat pea, is to be stuck upon the end of the pencil, by melting it, forming thereby a bulb, into which are to be inserted three darning-needles, by warming their eyes in the flame of a candle, and then burying them in the wax, at equal distances apart, around the circumference of the pencil, with their points extending about three-quarters of an inch beyond the end of it; but brought together so as to meet as accurately as possible at a common focus, forming the outline of a triangular pyramid: to secure them, another piece of wax, about the size of a grain of wheat, is to be placed midway between the bulb and the points, and secured there by melting it.
The very acute points of the needles are to be taken off by light rolling touches upon an oil-stone, and the raggedness, by a little fine emery-paper, so as to produce an obtuse, conical end; the pen, when thus completed, has of course a very fine triangular hole between the needle-points, through which the ink uniformly flows. We have seen some of these pens made by inserting the needles into drilled holes, made in metal, at the end of neat handles, in which the needles were so nearly brought together where they are inserted, as not to need the smaller bulb nearest to the points. The ink flows freely in them, and there is the same facility in using them as a finely-pointed H H H black-lead pencil. They answer well for tracing, as before observed; but we do not think them equal to the common forceps-formed drawing-pen for ruling clear lines.
Ruling-pens, for common use, are made by doubling a piece of tin-plate together, and rounding the ends, the middle being bellied for the reception of ink. Pens of this description were constantly used for ruling account-books, etc, previous to the introduction of the ruling-machine, which entirely superseded hand-ruling.
Ruling-pens for the machine are made of thin sheet-brass or latten, in long strips, the pens being cut on the edge, and folded together at various distances, according to the pattern to be executed.
Music-pens are made for ruling the five staves of music at once; they consist of a parallelogram of brass, terminating in five slit points, communicating with a small reservoir above, in which the ink is placed. They are fitted with a handle, in the hollow of which a small piece of brass is carried for cleaning out the ink passages of the pen. The accompanying engraving shows the construction of this very useful and ingenious apparatus.
Dotting-pens, for writing music, consist of a small brass cylinder, in which a pin of the same material works vertically, being kept down, and projecting about the tenth of an inch, by a spiral spring in the upper part of the pen. An elliptical opening, about halfway up the pen, receives the ink. When, placed upon the paper, the brass pin recedes, and causes the ink to make a round black spot on the paper, forming a note, - the tail being supplied afterwards with a common pen.