The Optical Magic Lantern Journal (May 1894)

104 The Optical Magic Lantern Journal and Photographic Enlarger. is quite right, and is marked 3; No. 2, which is concave on one side and convex on the other, is also right, but No. 1 is turned the wrong way about. With respect to your other question, you cannot get a disc of the same size from the two different positions with the same lens. In order to use the lantern from the back of the hall and obtain the same size of picture, you must have a lens of longer focus. Judging from the distances on your sketch, your lens is 54 inches in focus; whereas to use the lantern from the end and yet get the same size of image requires one of 10-inch focus. You might try your lens as follows, from the back of thie hall— Remove 1 and 2 altogether, and in their place substitute No. 3, placing the rounded size next the picture, and use limelight. Send 13d. and we willsend you a reference table. See diagram on page 92. R.S. H.—We did not receive the package spoken of. We make no charge for answering questions. Although correspondents who ask more than 5U per annum, usually send us a turkey at Christmas. Fuerst Bro.—We shall be pleased to receive the samples of Lumiere’s plates spoken of. Far East writes:—I make my own oxygen (because I have to), and have the following difficulties. Can you kindly help me. I use 2-lbs. chlorate of potash and 3-Ib. black oxide of manganese, and I havea bag 36x 20x 24. I have made the oxygen some ten times and have only once been able to fill the bag. The heat is from a «Little Hero" kerosene stove. I turn it down very low ar first, and after about twenty minutes the gas begins to come over; and after a time, the light being raised very slightly. the gas comes over violently. If I turn the light down, the gas soon stops generating, and I can get no more out of it, do what I will. I seldom get the bsg more than one-third full. Last time I used 3-lb. salt in addition ; this evidently controlled the gas, and it came over regularly, but as soon as the bag was about one-third full the action ceased, snd I could get no more gas. I raised the heat and I knocked the retort on a stone, but it was of no use. The books say that the mixture congeals at the bottom of the retort. Can you kindly help me by stating a remedy for this sort of thing ? When I set my mind on giving an entertainment I find I can get only very little gas. Which is the best to nse, powdered chlorate or that in crystals? When I last used my saturator it made a hissing noise and the light went right out; no pop or explosion. I lit it again, and although it gave a fair lightit jlickered all the evening, much to my annoyance. Can you kindly tell me the reason ? and then I can avoid it infuture. Doyou think I had too much ether in thie saturator? or was it caused by overflowing the ether in pouring it in the saturator? In this country (India) the ether evaporatcs so quickly that you have to fly round in pouring it in the saturator, and consequently it runs over when I put 5 oz. of ether in my saturator and leave it for an hour, no ether wiil come out when I turn it upside down and blow through the open tap handle, it seeins to be all absorbed in the packing. Last time I put 5 oz more (after an hour) and that too refused to come out. I then put in 2oz, more, and blew it through after a few minutes, Do you think I had too much ether in the or was the flickering due to the ranning of the ether in pouring it in as described above? Answer.—The heat given off from the stove you mention isinsufficient ; moreover you only obtain the oxygen from « small portion of the mixture for the heat given off from the oil lamp will only heat a narrow strip across the bottom of the retort. Better use such a lamp as we described in our issue for Febri:ary, on page 39. This will heat the retort evenly. You might increase the per Saturator, | over : centage of manganese, and use the chlorate in crystals. We have never seen & saturator behave in the manner spoken of. Twelve ounces:of ether is far too much, and perhaps you got @ quantity in the tubes which may bave caused the effect you speak of. You do not say whether you got good results by using the prescribed quantity only. Jas. Phares asks for the dimensions of cylinders of various sizes——The following are taken. from the list issued by Messrs, Lea & Son, of Runcorn, who are manufacturers : Bey oe rt 3 2 2 dig g/tv.je Els , iste, ae | ® 2 |e a5 2s¢| 255 | $884] 820 | 258 | $384 6 8; ¢2 8) s605|) 8 3s] se Ss! sass oO 3 = _ oO Qa ° im ~ aogr 5 }A 457 12 §]A AAs 5 3h. 11 20 4 30 6 34 123 30 4 42 10 4 15 40 53 30 12 4 18 |i 60 5} 45 15 4 20 || 80 bt | 60 } i 7 ——:0:—— THE editor of one of the leading journals in JAPAN calls the attention of his readers to the Orticat Macic Lantern JourNAL AND PuoroGRAPHIC ENLARGER as follows :— BAST A EE Ww BS q 5B O te i iit & HE: ' —~ ‘ FY fn ov eh o & Rt 43 (lms Yams [1 saN ar?