About the Construction of The Magic Lantern, or The Sorcerers Lamp.

We mentioned this kind of lantern on page 767 of Ars Magna Lucis et Umbrae and also, on page 793, displayed a method to transmit pictures in a dark room together with the colours necessary for their colouring with the help of sunlight; but in these instances we did also leave this, indeed outstanding, invention to be improved by other, greater inventors. And so it happened that many, attracted by this novelty, turned their attention towards its fulfillment. Most notable among these was Thomas Walgensten, a well-known Danish mathematician who, by reworking my ideas in those descriptions, produced a better form of the lantern that we described on page 767. He has later, with great profit, sold such lanterns to different Italian princes in such an amount that they now are almost everyday items in Rome. But there is no other difference between this lantern and the one we described than that the aforementioned Walgensten exposes several pictures in a dark chamber, with satisfactory clarity and elegance and with great admiration from the audience. In our College we use to show at most four, to great astonishment for visitors. The device is well worth to examine more in detail though, as it makes it possible to exhibit complete Satyric plays, tragedies and similar things in a natural way, without any interruption.

The use of a mirror in this new lantern, though, does not differ from what we demonstrated on page 793 of Ars Magna Lucis et Umbrae in other ways than that it is used in conjunction with a portable lamp while we use sunligth, reflected in a mirror on which images are painted, to display anything that such a portable lamp can display on a wall inside a room or a house, with natural rendering of the colours. We did also, at the same time, demonstrate methods of exposing pictures without the aid of sunlight, either with a concave mirror or a transparent lens. I have mentioned all these details so that the Reader may understand the origins of this new, mysterious lantern, that, as far as we understand, not undeservedly is called "The Magic Lantern" or "The Sorcerers Lamp" due to its remarkable capability to let the vision of any object come to sight in a dark room or in the silence of the night. After this opening we have nothing left but to give a short description of how it is constructed.

Make a wooden box, ABCD and attach a chimney to it so that the lamp may let out its smoke. The lamp itself should be placed in the middle of the box, either suspended by a metal wire or placed on a stand, M, opposite the hole, H. Place a tube with the width of a handsbreadth in the hole, mount a lens of good quality in the front end of the tube, I, and a well polished, flat glass in the hole or rather the rear end of the tube, H. On this glass you can paint any picture you like with transparent water colours. This will cause the light from the lamp, as it passes through the lens, to exhibit the picture that you have painted on the glass (which has to be placed in an inverted position) on a white-painted wall, VTSX, enlarged and in correct position with a natural rendering of the colours. Note that the light of the lamp has to be intensified; to accomplish this we place a bowlshaped, concave mirror, S, behind the flame as this will intensify the light in an almost incredible way. All this should be carefully considered, at least to some extent. Note also that the tube may point either inwards or outwards. Both methods are equally good so this is more a question of good judgment.

The explanation of the method to display multiple pictures remains. Put a well polished mirror glass between two thin wooden beams so that they form a parallellogram and join them carefully together. The width must be the same as the width of the hole, H. Make any paintings you like with transparent water colours on the glass, as seen on the parallellogram M,N. When this is pushed into the slits and moved from picture to picture past the hole H different images will appear on the wall. From this it is obvious that if you have four or five such parallelograms at hand, all with different pictures, it will be possible to display anything you like in a dark room. But I think that all this has been explained thoroughly enough, and that nothing more remains but to discuss the conclusions that can be drawn from figure II.

This sudden appearance of images will increase the astonishment of the audience even more if the lantern is placed in a separate chamber, ABCD, and the tube is mounted in the wall BD at H in the way that we have explained, because then any pictures that have been painted on the parallelogram (they may be joyful, sad, horrible, frightening and, for those who are ignorant of the cause of their appearance, even prodigious), will come to sight on the opposite wall, G, in the adjacent room BEDF together with any sentences and writings that have been drawn on the glass. But you will understand all these things better from the present figure II than if I try to explain it with a multitude of words. Thus, let us go on to other things.

From a copy of Ars Magna Lucis et Umbrae, Ed 2, Rome 1671, in The Royal Library, Stockholm. This translation © 1997 Mats Rendel.




Note 1

There is no mentioning of such a device on page 767 in any of the two editions of Ars Magna Lucis et Umbrae, so this must be either a printing error or a slip of memory. However, on page 793 of both editions, a treatise with the title Cryptologia Nova begins, in which Kircher describes a projecting device, called Steganographic Mirror and mainly consisting of a mirror and a lens. It was designed to use reflected sunlight as lightsource and the pictures were to be painted directly on the surface of the mirror. The reason for this was that Kirchers original intention was to use it as a part of a communication system, i.e. "optical television" or, rather, "optical fax". For this purpose he needed to have a very strong lightsource and the strongest one available was the sun. He had obviously great expectations for the future of his invention but was also aware of its limitations and practical diffculties: "The main problem is that the size of the enlarged images, e.g. of letters, increases enormously by distance, so that one single letter eventually reaches the size of a tower. Another problem is that the longer the distance is, the greater is the difficulty to distinguish these images, until finally almost nothing at all can be seen, except for in a completly dark chamber. Thus, if someone finds out a method by which he can transmit pictures over a long distance while keeping their size within limits, and also make them appear with enough clarity, then he will indeed have made an invention to be proud of!"

Kircher claimed he had been able to project a written message at a distance of 500 feet and that it could be read without difficulties (I see no reason to doubt this). He presented a calculation to prove that it would be possible to make projections at a distance of 12000 feet. This is probably exaggerated, but Kirchers projector is anyhow an interesting construction as the lens and the mirror, in order to reduce linear distortion, are independently adjustable in relation to each other, which makes it the first "optical bench" in the history of optics, predating its successors with some 150 years or so.

Note 2

Thomas Rasmussen Walgensten was born in Vallstena in Gotland, then a Danish province, probably in 1627. He was orphaned at the age of 10, when his father was executed for murder and he was adopted by relatives in Visby, the capital of the island. He attended the Cathedral School in Visby and was later sent to Copenhagen for further education. During a period around 1650 he held a Royal privilige to print almancs. Later he went to Leyden, where he studied mechanics and optics, and it was probably there he developed his version of the lantern. He made several tours across parts of Europe in order to market his invention and it is obvious from Kirchers relation that one of these tours included Italy, and that it was very successful. It seems also that he spent some time in France. After this he returned to Copenhagen, where he was appointed to be superintendent of the Royal Chamber of Mechanics. During his absence from Denmark radical political changes had taken place. Gotland had been conquered by the Swedes, together with all Danish provinces in South Sweden (and parts of Norway, too). In 1676, the Danish king decided to try to regain what had been lost, and declared war against Sweden. Though the Danes were unsuccessful at land (they were finally defeated by Charles XI in the battle of Lund in December 1676), they accomplished to take almost complete control over the Baltic Sea and to reconquer Gotland. Walgensten was sent to the island as vice governor and remained there until the occupation was over in 1677. (It seems, though, that he was allowed to keep his estate, Lilla Hästnäs). He returned to Copenhagen, where he soon became in charge of the design and building of the Royal Library. He died in Copenhagen in 1681.

Note 3

This, in conjunction with the accompaning illustrations, has been discussed since the the 1680:s. Everybody knows that the tube on a projector should be mounted on the outside of the case,"pointing outwards", and that the slide should be placed at the rear end of the tube,"in an inverted position". But if you look at the illustrations, you will see that the tube is mounted on the inside of the case, with the lens close to the lamp, while the slides are placed at the other end of the tube, in upright position. This would never work, would it? Didn't Kircher know what he was talking about? In fact, he did. This mystery has been solved by a Dutch scientist, W.A.Wagenaar. In his article "The true inventor of The Magic Lantern: Kicher, Huygens or Walgensten?" he writes:

After some experimentation the author recognized that indeed images can be projected with the arrangement of Figs. 1 and 2. If the lens has a very short focal distance (say less than 4 cm) a reduced image of the lightsource will be formed behind the the lens. If the reduction is sufficient the image could be used as a point-lightsource, projecting a slide without any interference of any further lens. The longer the distance between lightsource and lens, the more perfect the point-lightsource is. The farther the distance between point-lightsource and transparency, the less perfect the lightsource needs to be. And finally: the larger the transparency, the less critical the dimensions of the lightsource. Magnification will be proportional to the ratio of the distances from point-lightsource to screen and transparency.(From Janus LXVI, Leyden 1979)

This is obviously not Kirchers own invention, but maybe Walgenstens, as Kircher clearly implies that he is describing one or two of Walgenstens "new lanterns".