February 9. 1893] 



NATURE 



343 



I exhibit on the screen a circular letter summoning: a 

 Committee, that was written by the cyclostyle. The 

 writing seems beautifully regular when the circular is 

 photographically reduced ; when it is enlarged, the dis- 

 continuity of the strokes becomes conspicuous. Thus, 

 I have enlarged the word the six times ; the dots can 

 then be easily seen and counted. There are 42 of them 

 in the long stroke of the letter //. 



The appearance of the work done by the cyclostyle 

 would be greatly improved if a fault in its mechanism 

 could be removed, which causes it to run with very 

 unequal freedom in different directions. It leaves an 

 ugly, jagged mark wherever the direction of a line changes 

 suddenly. 



A much coarser representation of continuous lines is 

 given by embroidery and tapestry, and coarser still by 

 those obsolete school samplers which our ancestresses 

 worked in their girlhood, with an average of about six- 

 teen stitched dots to each letter. Perhaps the coarsest 

 lettering that is ever practically employed is used in 

 perforating the books of railway coupons so familiar to 

 travellers. Ten or eleven holes are used for each figure. 



A good test of the degree of approximation with which 

 a cyclostyle making 140 perforations to the inch is able to 

 simulate continuous lines, is to use it for drawing outline 

 portraits. I asked the clerk who wrote the circular just 

 exhibited to draw me a few profiles of different sizes, 

 ranging from the smallest scale on which the cyclostyle 

 could produce recognisable features, up to the scale at 

 which it acted fairly well. Here are some specimens of the 

 result. The largest is a portrait of \\ inches in height, by 

 which facial characteristics are fairly"well conveyed ; some- 

 whatbetterthan by the rude prints that appear occasionally 

 in the daily papers. It is formed by 366 dots. A medium 

 size is I inch high and contains 177 dots, and would be 

 tolerable if it were not for the jagged strokes already 

 spoken of. The smallest sizes are \ inch high and 

 contain about ninety dots ; they are barely passable, 

 on account of the jagged flaws, even for the rudest , 

 portraiture. 



I made experiments under fairer conditions than those 

 of the cyclostyle, to learn how many-dots, discs, or rings 

 per inch were really needed to produce a satisfactory 

 drawing, and also to discover how far the centres of the 

 dots or discs might deviate from a strictly smooth curve 

 without ceasing to produce the effect of a flowing line. It 

 must be recollected that the eye can perceive nothing 

 finer than a minute blurr of one three-hundredth 

 part of an inch in angular diameter. If we repre- 

 sent a succession of such blurs by a chain of discs, 

 it will be easily recognised that a small want of 

 exactitude in the alignments of the successive discs must 

 be unimportant. If one of them is pushed upwards a 

 trifle and another downwards, so large a part of their 

 respective areas still remain in line, that when the several 

 discs become of only just perceptible magnitude, the pro- 

 jecting portion will be wholly invisible. When the discs 

 are so large as to be plainly perceptible, the alignment 

 has to be proportionately more exact. After a few trials 

 it seemed that if the bcarino; of the centre of each disc 

 from that of its predecessor which touched it, was 

 correctly given to the nearest of the 16 principal 

 fKjints of the compass, N., NNE., NE., &c., it was fairly 

 sufficient. Consequently a simple record of the succes- 

 sive bearings of each of a series of small equidistant steps 

 is enough to define a curve. 



The briefest way of writing down these bearings, is to 

 assign a separate letter of the alphabet to each of them, 

 a for north (the top of the paper counting as north), b for 

 north-north-east, c for north-east, and so on in order up 

 to p. This makes e represent east, / south, and m west. 



To test the efficiency of the plan, I enlarged one of the 

 cyclostyle profiles, and making a small protractor with a 

 piece of tracing paper, rapidly laid down a series 



NO. 1215. VOL. 47] 



of equidistant points on the above principle, noting 

 at the same time the bearing of each from its predecessor. 

 I thereby obtained a formula for the profile, consisting of 

 271 letters. Then I put aside the drawing, and set to 

 work to reproduce it solely from the formula. I exhibit 

 the result ; it is fairly successful. Emboldened by this 

 first trial, I made a more ambitious attempt, by dealing 

 with the profile of a Greek girl copied from a gem. I was 

 very desirous of learning how far the pure outline of the 

 original admitted of being mimicked in this rough way. 

 The result is here ; a ring has been painted round each 



dot in order to make its position clearly seen, without 

 obliterating it. The reproduction has been photographic- 

 ally reduced to various different sizes. That which contains 

 only fifty dots to the inch, which is consequently six times 

 as coarse as the theoretical 300 to an inch, is a very 

 creditable production Many persons to whom this portrait 

 has been shown failed to notice the difference between it 

 and an ordinary woodcut. The medium size, and much 

 more the smallest size, would deceive anybody who viewed 

 them at the distance of one foot. The protractor used in 

 making them was a square card with a piece cut out of 

 its middle, over which transparent tracing paper was 

 pasted. A small hole of about \ of an inch in diameter 

 was punched out of the centre of the tracing paper ; 

 sixteen minute holes just large enough to allow the entry 

 of the sharp point of a hard lead-pencil were per- 

 forated through the tracing paper in a circle round the 

 centre of the hole at a radius of | inch. They corre- 

 sponded to the 16 principal points of the compass, 

 and had their appropriate letters written by their sides. 

 The outline to be formulated was fixed to a drawing-board, 

 with a T rule laid across it as a guide to the eye in keep- 

 ing the protractor always parallel to itself. The centre 

 of the small hole was then brought over the beginning of 

 the outline, and a dot was made with the pencil through 

 the perforation nearest to the further course of the out- 

 line, and this became the next point of departure. While 

 moving the protractor from the old point to the new one 

 it was stopped on the way, in order that the letter for the 

 bearing might be written through the central hole. 



A clear distinction must be made between the proposed 

 plan and that of recording the angle made by each step 

 from the preceding one. In the latter case, any error of 



