LivingPersons Represented on a Reduced Scale THE idea of projecting on a screen living figures larger or smaller than life was realized more than a century ago, but the weakness of the available sources of light made the representation very imperfect. Even the electric arc gives unsatisfactory results when lenses and a screen are employed, but by suppressing the screen and forming aerial images by means of concave mirrors, a very brilliant and realistic effect can be produced. An exhibition of this kind has been on view in Paris during the past year. At one end of a darkened hall is a little stage with a curtain about five feet wide and three feet high. The raising of the curtain reveals a “back drop” and side scenes of the usual type, and personages who move and speak in a very life-like manner, but are only twelve or fifteen inches tall. The following explanation of the trick, which we quote from La Nature, is conjectural, as the exhibitors refuse to give any information. The illusion is probably produced by two concave mirrors which are really above the floor, but are shown below the floor in the diagram, for the sake of clearness. The real actor, indicated by the arrow AB, stands before the mirror M, which forms a reduced and inverted aerial image of him at A'B', and the second mirror M2 forms a re-inverted and still further reduced aerial image at ab, on the stage, and in view of the spectator S. The rays which form the image pass through an opening in the back scene, and the part of the scene which is thus cut out is painted, on a larger scale, on a screen D, placed behind the actor AB. This part of the scene and a portion of the floor P are thus projected with the actor's figure. The actor's movements are necessarily restricted to a small area, but he can make gestures and dancing steps without getting out of range or focus. The illumination, as well as the distances, dimensions and positions, requires very nice adjustment. The actor and the projected scene D are necessarily illuminated by a powerful electric arc, while the back drop and side scenes of the little stage are lighted by rows of incandescent lamps, and the illumination must harmonize in order to produce a realistic effect. These difficult problems have been solved with wonderful success. Paintings Locked to the Wall THE stir occasioned by the recent theft of the “Mona Lisa” from the Louvre has drawn attention to the insufficient protection of paintings, which are simply hung on the walls of our great art galleries, ;ird can be detached by a twist of the hand on the part of a person more enterprising than scrupulous. The idea occurs naturally enough in some way to lock the paintings to the wall. This is what the inventor of the device shown in our illustration herewith does. A horizontal bar of rectangular cross-section extends along the wall, its ends being placed in bearings which allow the bar to rotate so as to present either its narrow edge or its flat surface in plan view. The paintings are provided with slotted ears, into which the horizontal locking bar can be inserted when in its “edgewise” position. The bar is then turned flat, and so locked by means of a lever (shown in Figs. 2 and 3). The picture is then held firmly to the wall. The device seems practicable enough, and should find extended use; though possibly to some tastes it may be objectionable, at least for private residences, on esthetic grounds. Mining in the Stone Age AMOST interesting glimpse into prehistoric mining in the Stone Age has recently been revealed upon the opening of the Oural and Aram copper-cobalt mines in Spain according to the American Antiquarian. "In these ancient Spanish mines,” states our contemporary, “the galleries and drifts do not open directly onto the mountain side. Instead they communicate with daylight by means of several vertical shafts or chimneys, a few meters in height. The purpose of thiEf arrangement was, it has been suggested, to effect a better control over the slave-miners. Perhaps, too, the purpose was to prevent wild animals from making their home in the mine along with the slaves. "Relics found both inside and outside the mine comprise bones, and various implements made of stone, bone, horn, fireclay or of wood. Among the principal relics found on the interior were sixteen skeletons, two of them complete; stone hammers; picks made of horns of animals no longer known in Spain; stone needle; torch sticks; a bone knife; two wooden bowls, Apparatus for projecting living figures on a reduced scale., and, strangely enough, some coins. The skeletons which were found belong for the most part to miners suddenly killed in the midst of their labor; the hand still holds the hammer, and occasionally a skeleton is found under a fall of rock. Other corpses met 'death in a cowering or crouching position. "All of the men must have been of extraordinary muscular development. The heavier stone hammers which they used weighed as much as twenty or twenty-two pounds. In spite of their muscular development, the majority of the miners were evidently of extremely slim build, for some of the galleries are literally polished by the rubbing of bones, and in these galleries, penetrating through the solid rock, a man of even small size can worm his way only with the greatest difficulty. The skulls have the appearance of youthful individuals or of children; but, considering th'E) differences in skull and brain development in thbse days as compared with to-day, this appearance may be deceptive. "The stone hammers, more or less polished, were often used by being held directly in the hand, without any sort of handle. In some hammers a wooden helve is preserved and in a few a thong served as handle. "For illumination, the miners used sticks of wood four to eight inches long. A ball of wet clay was rolled and slapped against the gallery wall. Into this clay the miner stuck his little light. Numbers of these wooden sticks or matches, the free end charred, are still preserved in place in their clay holders along the galleries. There are also found some resinous branches or twigs, wrapped in hide, and the latter soaked with grease or with resin. These. it is believed, also served for illumination; perhaps, too, for heating purposes. "Fire was used to splinter the rock, and to render it more friable and easier to attack. The clay along the vein walls was picked away by hand. Thousands of finger prints are still visible here; they show that the thumb of the miner of these days was of tremendous size, almost double the length of the thumb of present-day workmen. "No props were used in the workings, which fact alone proves that they antedated the Romans. In certain cases ore was extracted from the end of diggings into which to-day only a child would be able to penetrate. Several galleries are so steep and so slippery that any movement in them must have been with the help of thongs fastened into the roof of the gallery; in the-vertical stopes or raises there is usually still preserved a stone ring into which such a thong was fastened. "Originally, the ores were smelted in shallow, scooped-out hollows in refractory clay. These primitive crucibles were about 8 inches in diameter, and with walls 1% inch thick; fragments of them are preserved with ore, incompletely reduced, clinging to their sides. Later they must have employed a more highly perfected smelting device, for pieces of quite homogeneous slag are found; this denotes the use of some continuous smelting apparatus." Was Benjamin Franklin the First Inventor of the Lightning Conductor? TO some it may seem almost a sacrilege to raise the question which appears at the head of this note. Perhaps it may not be amiss to say right at the outset that investigation of the evidence leads to a substantiation of the ordinarily accepted view which gives to Benjamin Franklin the honor of having invented the lightning conductor. Nevertheless, it is interesting to note a number of passages in ancient literature and records, which have by some been construed as anticipating the modern method of warding off the lightning. This subject is discussed by an anonymous writer in Die Welt der Teclinik. Very soon after Franklin's invention became known, a French professor drew attention to ancient Tuscan and Romano/instructions, which spoke of “calling down” lightning (elicere), and further .pointed out that the ancient Romans had a regular rite for Jupiter elicius (Jupiter called down from heaven). It was argued, therefore, that the Tuscans and Romans knew, even at that early period, of the possibility of drawing down the lightning from the clouds. The Celtic nations also were in the habit of sticking their swords in the earth with the point upward, near springs, on the approach of a thunder .storm, as a protection 'against lightning. The Persian King, Artaxerxes, was acquainted with the power of iron to attract lightning. Again, Jo-sephus Flavius, in describing the great temple of Herod in Jerusalem, states that the roof was studded with an army of golden points, and that a similar arrangement was found on the earlier temples of Solomon and Zerubbabel. It is stated that none of these temples, in spite of their location upon an altitude, was ever struck by the lightning. Coming down to the Middle Ages, it is noted that an edict of Charlemagne mentions that the peasants were in the habit of setting up long pointed pole,.' in the ground on the approach of a storm, and in a sermon of St. Bernardinus of Siena it is mentioned that sailors would bind a sword with its point directed upward to the mast of their vessel on the approach of a storm. Apparently a very good case could be made against Franklin. Dr. Hennig, however, puts down all instances of this kind to pure superstition. The idea was to frighten away the storm demons by means of the upwardly-directed swords. Among uncivilized peoples it is a common custom to threaten approaching storms by the din of arms, and the ancient Gauls and Romans would shoot arrows into the gathering storm clouds, to ward off the hostile powers of the weather. As regards the golden points upon the temple at Jerusalem and other places, Josephus himself tells us that the purpose of these pointB was to keep off the birds