The Optical Magic Lantern Journal (October 1889)

Tho Optioal Magio Lantern Journal and Photographic Enlarger. 37. usually stated. A good lamp of this kind can be made to produce an illuminating power equal to one hundred and eighty candles, a Safety or Blow-through jet exceeding this by from ten to fifteen candle-power more. With mixed gases in one of the best burners it is possible to obtain a light exceeding four hundred candlepower. Two Hints to Workers with the Lantern. THERE are two qualities of chlorate of potash at present in the market—a cheap German make,-which can be sold at about fourpence per pound; and English made chlorate, which costs from sevenpence to ninepence. My advice is to eschew the former. Once or twice I have found it of fair quality ; but, as a rule, it is cheap and unreliable. Most workers with oxygen gas are troubled, more or less, by the tendency of the gas to come off in rushes, passing through the purifying bottles soj rapidly that it does not get properly washed. I find _ that the addition of a little dry common salt steadies the flow of gas wonderfully. My present formula is— Chlorate of potash, 1lb.; black oxide of manganese, 40z. ; common salt, 202. W. JEROME HakRIsoN, F.G.S. Lanterns and Accessories. —Ill. (Continued from page 29.) THERE was another very ingenious slide changer, patented I believe by Mr. Alexander Cowan as to the curtain effect, and Mr. Matthew Whiting as to the slide-changing apparatus, both well-known names in the photographic world. The slides are arranged in a box, delivering them one at a time to the carrier and passing them through the lantern, quite automatically, by the reciprocating movement back wards and forwards : ofa handle, the slides being delivered into another box in their proper order. The effect of changing arrange ment was that of a curtain falling over the picture and rapidly rising again on a fresh one. The apparatus was, I believe, brought out by Messrs. Houghton and Co, of High Holborn, London. Within the last few years what is known as the Lightning Carrier has hada great run. It isasold as the lantern, but has only lately been generally adopted, and therefore better constructed now than the earlier models. It may be briefly described as a skeleton holder with a stout rail of about five or six inches long at the top, and a similar rail of about twice thatlength ‘ether light to increase its brilliance. -| improves the light from four hundred and fifty to seven at the bottom. This is simply adjusted in the lantern and fixed there by the spring usually attached to the stage. The carrier, which slides in suitable grooves in the holder, is double—that is, there are two slits in the top rails, in which two different 3tin. slides drop into place in grooves made for that purpose. It is slid backwards and forwards across the field, registering more or less accurately according to the positions of slots at either end of its journey across the field. Usually, however, itis not at all accurately fitted, and the consequence is that when the one slide out of the two which it carries is being changed, the remaining one, then being shown on the screen, is very liable to ‘« jig.” The operator of course does not see this dancing of the picture, as he is too busy changing his views, but the spectators do, and they don’t like it. I would recommend any reader who has one of these carriers, and [ know of nothing better if carefully fitted, to take a little trouble with it by packing it so that it will work sweetly without any appreciable play in the holder. A simple way of using it is to cover the lens for a second while the carrier is being pushed across and uncapping as soon as thatis done ; but the best plan is to arrange a flap shutter, working noiselessly if possible, just behind the objective (front lens). It must hinge at the bottom and be square, then the effect will .| be that of a curtain falling on the picture and rising again in one second ona fresh one. The spectators will not x2se,aS was a printer’s error in the last word of article No. 1 for zzre. GEORGE SMITH. A New LIMELIGHT.—In a letter from Mr. A. W. Scott, of Weston-super-Mare, he says :—‘‘ I am now busy with a new limetight, which I hope to put on the market shortly. It consists of an apparatus charged with two different inflammable liquids (not ether), through which oxygen, from a gas-bag under moderate pressure (three 56lb. weights), is passed. This apparatus may be used as an accessory to the oxyUsed thus it hundred and twenty standard candles—the former (four ‘hundred and fifty) being obtainable with ether alone. The apparatus makes a corresponding increase with the oxy-hydrogen light (high-pressure mixed jet). In this case the coal-gas from a small bag is passed through the apparatus. The consumption of oxygen is increased and that of coal-gas decreased. But the best light of all is obtained by using the apparatus without ether and without coal-gas. I have not yet taken its candle-power, though | have used it for six public exhibitions. The working cost of the apparatus is one penny per hour. It is absolutely safe ; cannot be blown up, and gives less trouble than filling a bag with coal-gas in the ordinary way. I have the papers for provisional protection now in my hands. When arrangements for patenting, &c., are complete I shall be at liberty to give more details.”