SCOTOGRAPH, an instrument to en able a person to write in the dark, invent ed by Mr. John Isaac Hawkins, and in cluded in a patent taken out by him in 1803 for several other inventions relating to the graphic art.
Plate Scotograph explains the construc tion of this instrument. Fig. 1, is a plan of it ; fig. 2, 3, and 4, parts; and fig 5, a perspective view of the whole put toge ther. A BD E is a small box, covered with morocco leather, to be carried in the pocket ; its lid, F G, is made in two pieces, joined together by hinges in the middle, so as to turn back, as shown in fig. 5. and is kept shut by a small spring catch : a a (fig. 1.) is a small brass shell, fixed along one side of the box, at about one half of its depth from the bottom; it is also seen in the end section (fig.4) b de f, is a small pentagraph made of brass : one end of the rod, b. is jointed to a small hinge. g, by which its motion allows the whole pentagraph to be lifted lip : the other end of the rod, b, is jointed to the rod f, and the small handle, /a, or pencil, which the writer holds in his hand when in use, is attached to the other end by an universal joint, which allows it to move in any direction, to imitate as much as possible the motion of a pen : e and the other two bars, completing the pen tagraph i is the point which forms the letters; is screwed into the bar d: F G is a piece of wood glued to the bottom of the box, with a small piece of ivory fast. ened upon the top of it, to support the paper while it is written upon: the sur face of this ivory is about the same height as the brass shelf, a a, as is seen in the section fig 4.: H and I are two small rollers, (one of which is shown separately in fig. 2.) on which the paper is rolled ; it is fastened to them at both ends, by a small brass lever, k, (fig. 2.) which shuts down in a groove made in the roller : when the paper is put under this lever, and shut down, it is held fast, and by turning the roll is wound upon it : /m are two small milled heads, one on each roll, to turn them; at one end of the roll, 1, a small ratchet wheel, t, of six teeth, is fix ed; it is turned round by a click, k, (fig. 4.) jointed to a small lever, 1. which is thrown up by a spring, in : n (fig. 1 ) is a piece of brass plate screwed to the side of the box : it is shown separately in fig. 3. and has two branches, to receive the pi vots of the two rollers, II I; these arms are elastic, and press against the ends of the rollers, and cause them to turn ra ther stiffly, so that they will not be liable to be moved by the elasticity of the pa per which is rolled upon them. The pentagraph is of the common kind : the three points, g i, and the end of h, being all in one line, as explained in the article PENTAORANI : the point 4 which forms the letters, is a short piece of silver wire, screwed into the bar d, and pointed at the end to make this mark : the paper is rubbed over with whiting, or chalk ; and when at any time the point is worn away, it may be renewed by screwing it through the bar a little further : the point is al ways made to project so far, that when the blunt point at the end of the pencil, h, rests upon the brass shelf, a a, the pen tagraph will be set a little upon the strain, and by that means press upon the paper with a proper degree of force to write legibly. In using the machine,
the lid, F G, is to be half shut, as shown in fig. 5. and thus form a support for the hand while writing ; the pencil, h, is held in the hand, and pressed down to touch the brass shelf, a a, and used in the same manner as a common pen or pencil, tak ing care always to begin at the end of the shelf; the sideof the box, and a small ledge upon the edge of the shelf, limits the height of the letters. When the pen cil arrives at the end of the shelf, it is to be brought back again, and the end of it is to be placed upon the end of the lever, 1, and forced down ; the click, k, then takes into one of the teeth of the wheel, 4 and turns it round one tooth ; the pres sure is then to be removed, and the spring, m, lifts up the lever, 1, just the proper height to catch the next tooth of the wheel, as is shown in fig. 4: this ope ration moves the paper forward just the proper space to write another line. One of the uses of the pentagraph is to re. duce the writing to half the size that it is made on the brass shelf, whereby double the number of lines are contained on a slip of paper that would be if written the full size, and the lines are but half the length, so that room is left at the ends of the rollers for the ratchet wheel and milled nuts. The rollers will hold a slip of thin paper twenty inches long, and con. tain 100 lines, each of two inches long : this will contain a considerable quantity of information, and when it is all written and rolled upon the roll, I, the lever, k, (fig. 2.) of the other roller will be expos ed to view ; then the pentagraph is to be lifted up upon its and the lever raised up by putting the nail under the end of it : this releases one end of the pa per ; and by pulling it, the other roll will be unwound; and when the small lever of that roller is taken up, the paper.will be quite loose : another paper will befix ed with equal ease by first fixing it to the roll H, and rolling it. upon it, and then fastening it to the other. If at any time any particular line of the writing is want ed, it will be easily brought into view, by turning the rollers by their nuts, 4 m.
This instrument would be particularly useful to persons who have occasion to make memorandums while on horseback, or travelling in a coach, as any degree of pressure may be given upon the brass shelf while writing, so as to avoid being disturbed by the most violent shocks, which cannot be done upon common pa per for fear of breaking the pencil point, or of piercing the paper by it. Its use to blind people, who have learned to write, is very obvious.