The Optical Magic Lantern Journal (January 1891)

72 The Optical Magio Lantern Journal and Photograpio Enlarger. scries of photo-micrographic slides on the Bacillus Tuberculosis, asubject which is at present occupying the mind of Dr. Koch and other leaders of ‘nedical science. The set spoken of consists of twelve slides. * * a Tre manufacture of liquid carbonic acid gas is now carried onextensively. The washed and dried gas ispumped successively intoa series of receivers oradually decreasing in size until the gas is liquefied, which occurs when the pressure is raised to 36 atmospheres at a temperature of freezing point. . ” x A NEw form of light, which is said to be as powerful as the electric light, and the efhciency of which iy not impaired by fog, is obtained by a clock-work arrangement pouring powered magnesium at frequent intervals into the flame of a round wick lamp, producing a very brilliant flash of light. * 2 5 As we have not had an opportunity of trying the ~ Collins” hand camera since we received it, we must postpone No. 9 of Hand Cameras for Osiaining Slides for the Lantern until next issue. * * * Tr following paragraph has been going the round of the papers :—'t A panic was caused at a Ualonist mecting at East Coker, near Yeovil, on 17th December. A lecturer was showing some views by means ofa limelight lantern, when there was aloud explosion. ‘The people rushed to the doorway, a hissing noise from the lantern adding <. their fright. Ultimately, it was found that one af the cylinders in which gas was stored had cxploded.” But from information we have received welearnthat the connections at the gas bottle were net screwed down, hence when the gas was turned on there was a slight hissing noise, which was heard only by the few persons immediately around :}2 lantern, and that there was no panic. a 2 .) Mr. Auvreo UNDERHILL has resigned his position of hon. assistant sec. to the Croydon Cameta Club. The Lantern for Suffering Humanity. In last issue we suggested a scheme whereby hospital patients might have a periodical lantern entertainment. We are pleased to announce that offers have been made of cash, slides, apparatus and assistance. Those interested are hereby invited to attend a meeting on Tuesday, January 6, at 181, Aldersgate street, E.C,, at 7.45 p.m., in order to discuss the best means of conducting this worthy object. A Binocular Lanternescope. We recently inspected an instrument of the Lanternescope class which had been constructed with the intention of enabling one to view lantern slides in a maguified state, using both eyes, but when we looked at a slide through this instrument we saw nought but a confused picture. In the instrument spoken of, two small ordinary convex lenses were mounted at the ends of brass tubes attached to the box holding the slide. As far as fitting to one’s eyes, the tubes were perfect, but there their usefulness cvased. When the lenses were removed from the tubes and the eye applied, it was possible to see about two-thirds of the picture from cither side, and as the eye is applied at the centres of the lenses, part of the slide was seen by one cye and part by the other, hence one of the causes of the confused appearance. In a stereoscope, the lenses are so formed as to bend the rays coming from each picture inwards and upwards in sucha way that they enter the eye parallel, but when the picture to be viewed is a single one it is necessary that the rays be bent in the opposite direction before reaching the eye, at which time they must be parallel. The general principle by which two eyes may be used for seeing the one picture may be excmplified by taking a large magnifying glass and placing in contact with it a piece of brown paper or cardboard having two holes in it to suit the eyes, if then a slide be held at sufficient distance it can be clearly and distinctly seen with both eyes. As the greater portions of the glass spoken of arc covered, they are therefore useless for the purpose of aiding the vision ; consequently it will be apparent that only those portions opposite the: eyc-holes are required. Once of the best means of making an instrument with which both eyes may be used is by mounting a pair of plano-convex eye-pieces £4 inches 1n diameter of about 8 inches focus in conjunction with a prismatic lens of the same focus, each set separated the usual distance of the eyes apart. The prisms, which are of the same form as those instcreoscopes, are placed in the opposite direction to those in a stereoscope, and must be mounted so that the thick end of the wedges are presented to each other. The lens and prism together will give a focus of about 4 inches, at which distance the lantern slides must be stationed. Hoods should be placed on the outer end of cach lens so as to shade extraneous light from the eyes. With an instrument of this class, slides can be presented to the eye greatly amplified, giving the appearance of being projected on a large screen.