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History of Technology

Goodchild’s Trocheidoscope
Made by Horne & Thornthwaite, London

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Goodchild’s Trocheidoscope
8" W x 7" D x 7" H

In 1861, the Year-Book of Facts in Science and Art by John Timbs listed the trocheidoscope as follows:

This beautiful instrument has been constructed by Messrs. Horne and Thornthwaite, of Newgate-street, and is the invention of Mr. Thomas Goodchild, architect, of Guildford, designed for displaying various effects of the combination of colours upon a novel principle—some of them in a most brilliant manner. The Trocheidoscope is a train of wheelwork, so arranged that by gently turning the handle the horizontal disc table is made to revolve at varying speeds, at the will of the operator, from fifty to two thousand revolutions per minute. In the centre of the disc table is a carefully-fitted spindle, with a screw and flange at the lower end, and a shoulder at the upper end, just under which is a universal joint for adjusting the position of the topmost portion, upon which the patterns or devices are to be hung when exhibited. Proceeding from the side of the instrument is an arm of brass; with a small appendage or hook at the top for receiving the strings of the patterns, and a spring to act as a check upon the discs used in the Protean experiments. The spindle is jointed near the top to give a peculiar vibratory motion to the pattern when fitted. As the spindle revolves it strikes the sides of the circular hole by which the pattern is suspended, and so imparts to it a shaking motion just sufficient to fill up the pattern with all the colours on the disc below, but then lost to the eye by its rapid revolution. If the pattern were perfectly still, the colours would not appear; but if allowed slight motion as above described, the colours are reproduced upon the principle—that of images being retained upon the eye, which is thus elucidated in a very beautiful manner.
Described and Figured in the Mechanic’s Magazine.

As Timbs’ annual volumes described "The Most Important Discoveries and Improvements of the Past Year", it’s likely that the trocheidoscope was introduced in 1860.

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The instrument with the cover removed.
An adapter press-fits onto the output shaft, and either of two extension shafts may then be threaded into the adapter. 

The instrument produces a rotary output on the vertical shaft when the squared arbor is turned, presumably with a key or crank (not present).

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The gear mechanism. Turning the squared arbor causes the vertical shaft to rotate

The mechanism is not spring powered, but is geared up from the winding arbor to the output shaft.  The gear ratio is 40:1; one turn of the arbor produces 40 revolutions of the output shaft.

Websters’ Instrument Makers Database has the following information on Horne & Thornthwaite:

First formed in July, 1854 out of Horne, Thornthwaite and Wood; took Wood back as a partner, 1886-93; merged with Dollond and Co. Ltd. in 1913; W.H. Thornthwaite received a prize at the Great Exhibition of London in 1857.

Location: 121, 122 and 123 Newgate Street (1857-66); 122 and 123 Newgate Street (1867-74); 3 Holborne Viaduct, E. (1875); 416 Strand (1876-1912); all in London.”

The address on the instrument dates it to 1857-1866, consistent with the assumed date of 1860 from the Year-Book of Facts in Science and Art as noted above.

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The nameplate:
Horne & Thornthwaite
121 122 & 123 Newgate St. London

Knight’s American Mechanical Dictionary (1881) gives this description of the trocheidoscope:

An instrument designed for displaying the effect of the combination of colors. It consists of a whirling table operated by a crank, and painted of different colors, having a spindle arising from its center, by which are suspended disks having the outlines of various patterns cut out of them. The patterns are, one at a time, attached to this disk and to a branch projecting from the side of the table, which is rotated with sufficient rapidity to cause them to appear blended, though each is distinctly visible in the pattern disk, owing to its receiving a constant vibratory motion from the table. Were this not the case, the distinction of colors would not be visible.

- Mech. Mag., N.S. Vol. III. p. 268.


troch05.jpg (47323 bytes) troch06.jpg (52127 bytes)
The extension shafts.
The top section of the one on the right appears to have a ball and socket connection to the lower part.

Other Sources:

Horne and Thornthwaite published an undated 16-page booklet on the trocheidoscope "by the inventor, Thomas Goodchild, Architect, Guildford", titled: “A description of the trocheidoscope, an optical instrument for displaying various beautiful effects of the combination of colours, upon an entirely novel principle, with numerous interesting, and brilliant experiments”. The booklet gives a price of £2 2s 0d for a trocheidoscope "In neat polished Mahogany Case, with an assortment of one dozen Discs, and Instructions for use".

The text and illustrations of this pamphlet are shown below.





An Optical Instrument


C O M B I N A T I O N   O F   C O L O U R S,




Opticians, Philosophical & Photographic Instrument Makers to Her Majesty,
121, 122, & 123, NEWGATE STREET, LONDON, E.C.






Optical science affords many pleasing and instructive exhibitions; its very spectacular nature always rendering it attractive.

The attention given to this science by the most profound philosophers from the earliest times, has tended to advance it very considerably, and its signal importance in the study of Astronomy alone, gives it a very conspicuous position amongst the natural sciences.

It is not only, however, in its use by the employment of magnifying or other lenses, or by other catoptrical or dioptrical media, that pleasing and useful facts may be eliminated—nor by the simple use of nature’s unbroken light only that wonders can be deduced, but the origin and effect of colours, and the duration of images upon the eye, afford interesting matter for investigation and study, and have received some attention from learned opticians.

It is a well proved phenomenon of the organ of vision, that an object presented to it will apparently remain in view for a short period of time after the object itself has been removed—that a "spectrum" or representation of the figure takes the place of the figure itself without any perceptible break. It is like, indeed, a photograph of the object, retained upon the "retina" or mirror of the eye for about one-seventh of a second.

This may be proved very easily, as follows:—Put a few coloured counters or coins in the hand and close it,—suddenly open and shut it; the impression of the counters or coins will be left so distinctly upon the eye, that you can, with a little practice, count them after the hand has been removed.

Houdin, the Conjuror, tells us that from practice he could tell the number and position of all the articles in a shop window from one glance.

Many instruments have been devised to illustrate this peculiarity, the simplest of which is the Thaumatrope. This consists of a card, having, say a horse on one side and a jockey on the other, a silk string is attached to each edge, and by twisting these round, both sides of the card appear visible at the same time, and the horse is bestridden by the rider; or part of a sentence may be written on one side and the remainder on the other—when twisted, it will be complete, and may be read; the impression being retained upon the eye and conveyed to the brain at the same moment.


There is also the Stroboscope, well known to frequenters of the Polytechnic; it is a disc upon which figures are drawn in various positions; round one side slits are cut, through which you look at a reflection of the figures in a looking-glass. When the disc revolves, the figures appear dancing, playing at leap-frog, &c.—the figure last seen being connected with that which has gone before, by being retained upon the eye.

There is again the “Colour Top,” an instrument wherein colours are disposed in sections upon a horizontal disc with a vertical spindle; it is wound up with string after the manner of a humming-top. The rapid revolution caused by spinning effects a blending and apparent loss of the colours. This instrument has been improved by J. Gorham, Esq., of Tunbridge, who applies open pattern work over the coloured disc, in ft state of revolution also, which effects a certain breaking up of the colours, and produces many beautiful combinations by a species of invisible shaking during revolution, which allows the colours to remain upon the eye for a short time, as before explained.

The construction and manipulation of this primitive instrument of course renders its adaptation to practical requirements out of the question; still the effects are very beautiful, and afford some scope for study and design.

Before proceeding further, it may be desirable to say a few words upon the nature of light and colours.

Good ordinary day-light is composed of seven colours, which may be perceived in the rainbow, and are commonly called the prismatic colours. They are:

Violet     Indigo     Blue     Green     Yellow     Orange     Red

When the light is dissected by the prism (a triangular block of glass similar to a chandelier lustre), these colours become visible very clearly. All natural objects have the same effect upon white light, so dissecting it, that they exhibit to us the colour of which we say they are composed, as blue, red, green, &c., as the case may be—depending upon certain laws of refrangibility of the rays of light for the colour they possess.

The seven colours before mentioned are known as the primary colours; they are by some reduced to three elementaries, red, blue, and yellow, as the others may be composed of them, thus:

Blue and yellow
Blue and red
Red and yellow

There are certain colours which have the proper natural contrasting or accidental colours, and others which harmonize with them. A knowledge of these is absolutely necessary to all who have to do with the use of colours for any purpose, either in decorations, or in leading the public taste in the matter of dress, paper-hangings, upholstery, &c. &c., as upon a proper assortment really depends the general effect upon the eye, as to whether it be pleasing, satisfactory, or otherwise; a judicious combination according to the rules of contrast and harmony only being in true taste.

Buffon gives a very simple experiment in illustration of natural contrasts:—Place a red dot or wafer upon a sheet of white or black paper, and look at it steadily for a few seconds; on removing the eye to a piece of white paper, a green dot will appear—the proper contrast to red.     






violet with a
    little red

Natural harmonizing colours are those which are found next the originals in the order of the Spectrum. Hence, yellow will form the harmonizing colour to white, orange to yellow, red to orange, violet to red, &c.

In order to elucidate these remarks and the experiments which follow, I here append a “Spectrum” shewing the colours in their natural order.


The contrasting or accidental colour may easily be found from this diagram Bisect the containing angle of the section of which you want to find the contrast, produce the line, and it will cut the accidental required; thus, violet angle will cut through green; indigo, orange; blue, red; &c.

Complementary colours are those which make a white when mixed by rotation. Now the whole of the colours of the Spectrum, arranged as shown in the diagram, form white when rotated, illustrating at once the nature of white light. If we remove one of these colours, say violet, by covering it with black, a green tint will be produced—when rotated, its accidental. And so by obtaining the accidental we are enabled to replace the original and complete the circle. We also know by this means what colour is absent.

In the course of the experiments, I shall endeavour to describe some very simple methods of obtaining accidental and compound colours which afford Many instructive data of the laws which govern the arrangement of this nature tinting; and also develope some very pleasing and indeed wonderful combinations, graduating from one tint to another in the most imperceptible manner, and which may be rendered of great practical use in all cases where harmony of colour is desirable, affording, at the same time, an important educational medium for instruction in the properties of light and colours, and the power of one colour over another, and how one colour may be absorbed by contact with its really powerful neighbour, though apparently of less magnitude.


In the above Diagram a side view of the TROCHEIDOSCOPE is shewn.



Chamber containing the motion work.
Disc table for coloured patterns.
Pattern to be exhibited and coloured.
Spindle with joint and upon which
the pattern is hung.
Is the check spring, and




Hook for holding the pattern
Is the stand and drawer for
patterns, and
Is the handle by which motion is
imparted to the machine.

The TROCHEIDOSCOPE is a train of wheel-work so arranged, that by gently turning the handle (H) the horizontal disc table (B) is made to revolve at varying speeds at the will of the operator, from fifty to two thousand revolutions per minute. In the centre of the disc table is a carefully fitted spindle, with a screw and flange at the lower end, and a shoulder at the upper end, just under which, is a universal joint for adjusting the position of the topmost portion upon which the patterns or devices are to be hung when exhibited. Proceeding from the side of the instrument is an arm of brass, with a small appendage at the top for receiving the strings of the patterns, and a spring to act as a check upon the discs used in the Protean experiments.

The spindle (D) is jointed near the top, to give a peculiar vibratory motion to the pattern when fitted. As the spindle revolves, it strikes the sides of the circular hole by which the pattern is suspended, and so imparts to it a shaking motion just sufficient to fill up the pattern with all the colours on the disc below, but then lost to the eye by its rapid revolution.

If the pattern were perfectly still the colours would not appear, but if allowed slight motion as above described, the colours are reproduced upon the principle described in the first portion of this pamphlet—that of images being retained upon the eye, which is thus elucidated in a very beautiful manner.


Some patterns will require the spindle to be depressed more than others, as will he shewn further on. It forms in reality a wheel, the spindle head representing a cog in the edge of it, and which, as it rotates, attempts to carry the pattern with it, but is prevented doing so by the string holding it back.

The discs for the experiments and for imparting tints to the patterns, are circular pieces of cardboard, with the colours disposed in sections in various proportions and forms, and with a hole in the centre to receive the spindle screw.

Fig. 1.


Fig. 2

Fig. 3.

These discs form the basis of all the experiments, and may be coloured, or (what is better and neater) covered with coloured papers, radially, spirally, concentrically, &c. for the multifarious effects, and which may be made by amateurs to meet various experiments; the aim of this pamphlet being to lay down first principles, working out a few of the effects by way of example.

The perforated patterns are made of blackened cartridge paper. The pattern is to be sketched


upon the white back, and is then easily cut out with a pen-knife, or punched out with a hollow punch; very small perforations may be made With a stiletto. A hole should be cut for the spindles, in the same position as in those sold with the machines, and a piece of twine or silk cord passed through a hole in the opposite edge to fit into the hook and hang a little loose.

To arrange the Instrument for shewing Patterns, (&c.—Unscrew the spindle and put down a coloured disc, screw on the long spindle and mount a perforated pattern, hook the string on to the check arm (always keeping it and the bottom edge of the black pattern clear of the coloured disc), then revolve gently at first. It is advantageous to let the coloured disc have plenty of light upon it, therefore it is as well to manipulate near a window in the daytime, and to shade the top of the black pattern with your hand or a Chromascope. Regulate the top of the spindle to suit the pattern, the more colour you wish to shew the more the spindle will have to be deflected. A little practice will soon shew the right inclination and speed to suit particular patterns.

In order to illustrate the principle of the spindle, mount a black disc with one hole in it, some one-tenth of an inch in diameter (A. Fig. 7), over a coloured disc with four or five colours; deflect the spindle head very slightly, and rotate. The hole will be enlarged to thrice its diameter, (as B. Fig 7), with a black centre, and the colours of the disc below shewing in regular order round


Fig. 7.

the edge. Deflect the spindle a trifle more and the one hole becomes a ring or band some half inch in diameter, with the colours disposed as before, and with a large black core or centre (C. Fig. 7), the ring also will appear to stand out from the card in a very singular manner, having an appearance of solidity, the colours always appearing in the same place and perfectly distinct. With two holes the appearance is as shewn at D. Fig. 7. Thus with a few holes a very pretty pattern may be made.

A hole made with a common pin shews all the colours, only more minutely. As a rule, the larger the perforations in the patterns the more will the spindle require to be deflected; and with a very finely cut pattern, it will require to be nearly perpendicular; it can, however, be adjusted to the greatest nicety. And, when the spindle is quite perpendicular, Mr. GORHAM’S revolving patterns* can be exhibited in the most perfect manner. These patterns are cut in black paper, with a hole in the centre, and revolve with the colours below; the former being retarded by strings attached to the edges, and, so causing the colourings to appear to the eye clearly and beautifully.

* These patterns being patented are not supplied with the instrument, but can be obtained of Mr. Gorham, the patentee.


The original pattern, however, being entirely merged into one more intricate and complex, and being shewn quite horizontal, the colours are partially shaded, which is not the case with patterns hung at an angle on my principle. Again, by the non-revolving patterns, the design is coloured and enriched, and does not lose itself in the movements before the eye, which gives the Trocheidoscope a great advantage, and renders it of immense practical value in the formation of designs, which may thus be tried in the instrument with various colours, and thence committed to paper, and the result worked out in fabrics, decorations, &c., as the case may be, in endless variety, as also in the representation of every kind of ornamental work, mosaics, tiles, parqueterie, &c. All that is necessary is to cut out the original pattern, then trace it upon a sheet of paper, and touch up the drawing so made, then put the desired colours upon the disc table, mount your black design over it, and rotate; then you can mark with a pencil on your drawing the position the colours assume, and tint it in the usual way. The colourings can of course be varied by changing the coloured disc.

Thus suppose you sketch a design for a geometrical pattern to appear in blue and gold—screw on a disc, half blue, half yellow, mount your pattern, and rotate. The colours will shew themselves, not mixed, but artistically arranged; then if you would prefer the pattern in, say red, blue, and yellow, put on a disc with these colours in equal proportions, mount your pattern and you will have it so coloured.

The contrasts and harmonies may thus be tried to any extent, and their effects elucidated without the trouble of water-colouring a design.

Before proceeding to the experiments, I will enumerate some of the principal effects produced by the instrument:‑

1st. Blending the radials or wedges of colour by revolution at various speeds, thus producing one or more compound colours. This is the simplest form of experiment, and many beautiful effects may be obtained, colours mixed, &c. Various forms giving a graduated or " shot " appearance if a coloured spiral be introduced over the radials so as to cover some of them; the tints of flowers may be imitated, softened into one another as in nature. By using two semi-discs, say of red and blue, the power of one colour over the other may be ascertained by altering their proportions, slipping one more under the other, &c., and any desired tone of blue, red, or purple may thus he obtained. Three or four of these different colours may be mounted at the same time, and by loosening the spindle their position may be shifted, and the effect and colour altered accordingly.

2ndly. From one colour and white eliminating another totally different or accidental colour.

3rdly. While the colours are apparently lost to the eye by the revolution of the disc, so superadding a blackened disc in which is pierced a device or pattern, that the colours shall shew through the perforations and fill up the pattern with many singular and beautiful combinations of colour, and in many instances eliminating colours which do not exist on the disc below.

4thly. The reproduction of colours on die disc while revolving, by partially covering some of them with black shaders, as Figs. 12, 13, and 14, to shew the colours in bands, spirals, and other devices, so producing really marvellous combinations, which, by a simple mechanical means, may be instantly changed, forming other and curious effects and combinations of colour from the same discs in infinite variety.


Fig. 12.


Fig. 13

Fig. 14.

This class of experiments illustrates the combinations of colours, and the effect of black revolving over them at the same speed. The effect is produced by retarding the black disc for a moment, which, in effect, shifts its position on the colours and allows them to be seen in different proportions, producing combinations of the most beautiful description, merging one colour into another in a manner totally impossible by any other method; the alteration of one-twentieth part of an inch, giving a new set of shades, which may be rendered of great practical value. In many instances, the complementary and compound colours are eliminated at the same time, so that not only the colours actually upon the disc are seen, but others which are produced to the eye, filling up the openings with tints of great richness.

With a, view to assist in developing some of the above enumerated effects, I append some of each class of pleasing and instructive


Class I. Screw down a disc tinted equally light red, dark red, blue, green; rotate; the green will predominate, shewing the power of that colour over the others, and the weakness of the red.


2. Put down a disc with the seven prismatic colours in the proportions shewn in the Spectrum, white will be produced.

3. Put down disc as Fig. 2, a shaded flower-like tint will be produced.

4. Put down a disc, with a spiral gummed over in various colours, a shaded effect will also. appear.

5. Fig. 3 will shew a beautiful self-coloured centre (of whatever colour the heart may he) and shaded border.

6. Mount a disc, half blue, half yellow, you cannot obtain a green, although these two colours make green; but,

7. Mount a disc coloured equally red, blue, and yellow, so that holding the yellow, you have the blue on your left and red on the right, thin the handle gradually overhand away from you, and you have a reddish orange; let this cease, and turn the disc very gently the reverse way, a decided green will thus be produced. Note—this colour it has hitherto been found impossible to produce from other colours, in revolution with the " Colour Top," or any other instrument of the kind. It is a curious fact that it is only produced when the disc is turned one way—the yellow seeming to wait (so to speak) in the eye for the blue to mix with it, the red giving a tone to the whole; the more there is, the brighter the green—and red is the accidental to green! So of the first portion of the experiment, orange is composed of red .and yellow, and blue is the accidental to orange. By this experiment, two of the prismatic colours are evolved from what some hold to be the three primaries, but two alone will not produce them without the third or accidental in some proportion.

8. Screw down a disc tinted in concentric bands like a target, the colours instead of blending will each appear more clear and distinct.

9. A curious effect is produced by having a disc coloured partly radial and partly concentric, the radials disappearing by revolution, and the concentrics becoming more apparent.

Class II. Experiments for the evolution of accidental colours executed with discs, half colour, half white, in the performance of which several singular phenomena present themselves. The short spindle to be used for this and the fourth class of experiments.

Fig. 11


10. Screw down a disc half blue and half white, and with it a black shade as shewn in Fig. 11, rotate with some speed, and the outer ring of black will become a pinky orange—the accidental colour to blue; turn the shade half-round, so that the outer ring is over the white part, on rotating it will appear of a deep blue, while beyond the shade it is of a very undecided grey colour. Thus, half a ring of black preserves the blue colour during rotation, while, when over it, it is a, pinky orange.

In the same way colours may be produced as follows, viz.: with


Red and white
Yellow and white
Orange and white
Green and white
Indigo and white
Blue and white 
are produced
cold violet
dark purple
very light violet
yellowish orange
pinky orange

From analyzing experiments, Nos. 12 and 15, it will be seen that the dark colours are produced from light originals, and vice versa. It will be noticed how nearly these colours tally with those given by Buffon in his wafer experiments; but in this case they are more decided and more easily perceived; they also agree with the formula given to find the accidentals on the Spectrum. Other colours may be produced in a similar way.

Class III. These are for practical purposes, colouring designs, &c.

From an inspection of the diagrams, 4, 5, 6, 7, it will be perceived that great variety of devices can be exhibited. (The formula for mounting these is given on page 8.)

Fig. 4.

Fig. 5.

Try No. 4. Put down a disc with five or six colours. (Note—discs with more than seven or eight divisions of colour are of little use) and mount the pattern; deflect the spindle very little and rotate gently at first, and gradually faster until the colours shew distinctly and brightly, when do not increase the speed. This is an elegant pattern for a table cloth centre, or for a panel, &c.


17. Try the same pattern, No. 4, with a disc, half blue, half yellow, and it. will be very pretty.

18. Mount the butterflies shewn in Fig. 5, with four or five colours; they will appear very beautiful and with life-like motion.

Fig. 6.

19. Discs as diagram 6, with the spindle hole in the centre, are also shewn in a similar manner—being prevented from rotating by attaching the check-string to the wire E, Fig. 1.

20. Mount a disc (Fig. 9,) over half green, and half yellow; the more the spindle is deflected, the more the colour will shew, and it will appear as Fig. 10—


Fig. 9.


Fig. 10.

the periphery striped with light green and yellow, and the little spokes converted into double crescents, the one half of each coloured dark green and the other orange red. This is very pretty with various colours.


21. An imitation of a natural phenomenon. Screw on disc with the seven prismatic colours, and mount Fig. 8; rotate, and a RAINBOW appears to view, coloured and blended as in reality.

Fig. 8.

In the class of experiments for shewing patterns, I would suggest a few subjects as suitable for exhibition, most of which I have tried:—flowers, fruit, wreaths, ornamental china, aquarium with fish, &c., stars for illuminations, fashions, harlequin, waterfall with rainbow, concentric rings, geometrical forms, prisms, &c. birds, parrots, peacock with spread tail, necklaces, jewellery, coronets, crowns, parqueterie, illuminated letters, patterns for wall decorations, dresses, furniture, &c. &c.

Fig. 15.

Fig. 16


For showing jewellery, precious stones, &c., and for obtaining particularly brilliant effects for other devices, I have used the metallic paper. I found, however, this of little avail if used flat, the colour was only visible at the angle of reflection, at other points the light was simply absorbed. I had therefore recourse to a stratagem to render it subservient to my requirements. I succeeded in this by corrugating it, as shown Fig. 15, thus giving endless surfaces to the light, by which the picture is fully coloured in every part.

A shade is sometimes advantageous in viewing the patterns, as the colours then appear more brilliant than ever. A convenient form is shewn at Fig. 16, and consists of a hollow cone, twelve inches long, and six inches across at base,. black inside. The larger end should be held about half an inch off the black pattern, and the eye is to be applied to the smaller end. This Chromascope is particularly useful for viewing horizontal patterns.


Class IV. 22. Turn we now to another class of experiments of a very interesting, amusing, and instructive character, having the effect of magic, and by which one’s friends can be surprised as well as delighted.

Put down the disc with the prismatic colours, and upon it the black shade, No 12, screw the spindle down so loosely that the shade may he freely moved over the colours with the finger. Provide yourself with a quill feather or light stick as a wand. You will notice the projecting spokes at the sides, which when revolving are invisible; rotate, and you see hands of certain colours; then just bring your wand in contact with the spokes, this will change the colours; again touch, another change is effected, and so on in great variety. This not only shows the colours themselves, but also the complementaries, compounds, &c. With the same shade the colours will shew in distinct bands, and each prismatic colour may be shewn in regular rotation by allowing the spokes to strike the wand gently during revolution.

23. Now try Fig. 13. Here on rotation you have the colours merging one into the other, which by the wand may be made to change often and again; many other forms cut in the black give very singular and beautiful gradations, and a great many experiments may be tried in this class.

24. Fig. 14 is very beautiful and clear, though produced from such simple means, the colours (by contrast) appearing very brilliant; other forms may be tried with equal success, as parabolas, o-gee, or wavy lines, part spiral and part concentric cuts, &c.

25. A puzzling effect may be produced by having two black shades, one with two rings cut in the outside only, all the black being cut away in the centre, except four arms and the spindle hole, and over this a smaller one with three rings cut in, and about three inches diameter in all, this latter must have a small portion standing up to catch the tip of the wand; mount these loosely and rotate; by touching the spoke of the outer one, the outer colours will change, then by touching the projecting portion of the smaller one, the colours next the spindle will be changed, and so an endless combination of tints may be evolved.

26. It is very interesting to mount the small shade by itself, and cause the changes as before; the colours are very fine and endless.


27. Screw down a coloured disc, (Note—always use the short spindle in the Protean experiments), and drop a black shade over the spindle; on rotation, the colours will gradually change by themselves without touching, and shew some curious combinations.

For the information of those who would like to mount coloured discs with papers, and to black their own disc paper, I append the following directions:

Coloured discs. Cut out your papers in the sections or forms required, and fit them carefully upon the foundation (of stiff paper), then cover the foundation paper with good gum water, not too liberally, and gently place on your coloured papers, pressing all down together with blotting paper; put under a press until dry, then trim the edges, and cut out the spindle hole.

Black disc paper. Dissolve lamp-black with hot water to the consistency of a thin paste, then add gum water or very thin glue, stir it well to break the clots, then spread it over one side of good cartridge paper with a flat brush; when thoroughly dry it is fit for use.

Guildford, 1860.  






Opticians, Philosophical & Photographic Instrument Makers to Her Majesty,

121, 122, & 123, NEWGATE STREET, LONDON.

 PRICE: In neat polished Mahogany Case, with an assortment of one dozen  
  Discs, and Instructions for use £2 2 0
            Extra Discs, per dozen 0 7 6

Copyright © 2007 FTL Design

Last revised: 2 July, 2007

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