Moving Picture World (Jan-Mar 1914)

THE MOVING PICTURE WORLD 807 Another Experiment. John Griffiths, Ansonia, Connecticut, is here with the following: This letter is not in the nature of an argument as to who gave the correct answer on the glass heating matter. I admit that I was barking up the wrong tree myself. However, anything which tends to increase our knowledge in matters connected with our profession is worth finding out. (Righto! Ed.) And now I am going to suggest an experiment which will cause even more surprise than the glass stunt. Take an ordinary thermometer, having an exposed bulb, and put it in the cone of the lamp ho-use for fifteen seconds, with the bulb within one-half inch of the hot condenser, and note the degrees rise in temperature. Now, after allowing the thermometer to cool down to its original temperature, hold the bulb in the light rays near the aperture and you will find that near the aperture is by far the hotter place (that is where the glass surprise came in. Ed.), which seems to prove, beyond doubt, that my reasons why the glass in the slide carrier got so hot were ■correct. The experiment with the thermometer should be made when everything is good and hot, say at the close of the show, but if you have any respect for the thermometer keep your eye on the mercury when the bulb is in the light ray at the aperture. Vou can leave it close to the condenser for one full minute without damage, provided it is not actually touching the lens, but half -a minute near the aperture would cause the bulb to explode and that fact ought to satisfy Brother Foltz, Findlay, Ohio, that there really is some heat there after all. I am not yet prepared to accept the theory that the greater part of heat rays, as effecting glass, are extracted when light passes through the first glass. I would not think of disputing that proposition, but I am inclined to believe that a glass becomes hot exactly in proportion to the amount of light it absorbs. (Hum! that is worth thinking over some. Ed.). A piece of mica is not so clear as glass, therefore, it would absorb more light and get a little hotter, and if another piece of mica were placed so as to intercept the light ahead of the first one, then the second piece would naturally not get so much heat, since it would not receive so much of the light. Now here is something not generally known: A piece of tinned iron would not get as hot as a piece of black iron, because, although the tinned iron stops just as much light as the black iron, the tinned iron reflects a large portion of the rays back again, and the iron only gets hot in proportion to the amount of light it absorbs. For proof of this last statement cover the bulb of an ordinary thermometer with a piece of black iron and another thermometer with a piece of tinned iron and in both cases have the back of the iron touching the bulb of the thermometer. Now hold each one in the rays of light for the same interval of time and the one with the black iron will register the greater amount of heat. Vour last statement is, to my mind, not correct, in as far as light be concerned, neither of the pieces of metal absorbing any light whatever. It is, however, a fact well recognized by those who have to do with heating that an iron radiator painted black will radiate more heat than one covered with silver bronze or any light color and, conversely, black iron will absorb more heat (not light, mind you, but heat) than when painted white or a light color. Of course, I must admit that the question of light rays and heat rays are here to some extent jumbled together, and pretty closely inter■woven. I have not the space now to go into this matter extensively, but it is interesting and, as you say, anything which tends to give us an enlarged knowledge of anything having to do with the operator's profession. ■or' line of work, is of distinct value. That is one difficulty the editor of this department is now contending with. It is a perfectly simple matter to get almost any operator to see the value of knowledge which will hel|' "him, for instance, to stop his picture from vibrating on the screen, but it is not every operator who can see and understand the fact that discussions of this kind also have a very decided and distinct value in the broadening of knowledge. It is the desire of the editor of this department to co-operate with the ■more advanced men, gradually, so far as possible, dropping the answering ■of simple, kindergarten questions, and to devote the department almost •wholly to matters of higher class. There are hundreds of matters, some of them purely theoretical, some of them practical, and some of them a •mixture of theory and practice, which can be profitably discussed. Neither this department nor its editor has any apology to make for its course in the past. If it was all to do over again I cannot, in looking back, see where I could have modified to any material extent, what I have done, taking ■everything into consideration. What the course of the department will "be in the future will depend to a considerable extent on the co-operation ■shown by advanced individual operators and by operator's organizations. Meanwhile, let me say to Brother Griffiths that discussions and experiments as he has set forth in this letter will always be welcome, and will be -given space so far as is practicable in the present "very crowded condition -of the department. made orders sent to the editor of this department, accompanied by money order in the sum of $2, will be taken care of, and, in view of the questions now running, I would again strongly recommend all operators to invest that sum in Mr. Swoope's work. From Canada. Charles S. Stuckey, Edmonton, Alberta, Canada, writes: I guess I had better wake up and take a little more interest in your series of questions, which will undoubtedly prove of great help to many operators. Attached find my answer to Question No. 12. Am now operating at the Monarch Theater in Edmonton. Our outfit consists of a combination Power's Six and a dissolver with a G. E, rectifier for the projector and a rheostat for the dis ^.J ^^^^^^^^^^^^^^^3^^^^^ M ^hh^ l^iii£j^_is»9<iniflH solver. We pull 35 to 40 amperts at llie arc and get very good results on our 1 2 5foot throw, projecting an 18-foot picture on a plaster wall covered with some special coating. I enclose picture of my operating room taken by myself while my partner, David M. Stimac, was running the machine. I am sorry, old man, but your reply to Question No. 12 came too late. Get a hus-tle on. You are not the only one those questions are waking up and showing how little they really do know when it comes right -down to the technical side of their business, and just you wait! Some of the questions already asked are easy compared with some of them yet to come. The motor, generator and engine will last fully six months or more, probably considerably more, and tliere are some very pertinent questions to be asked which I think will put even the best of you to grubbing. But let me tell you, friend Stuckey, that the compilation of this series of questions is proving to be one great big task. I had no idea what a job it really would L^rove to be or perhaps I would not have tackled it at all. Carbon Resistance. Brooklyn, New York, writes: My employer is also an operator, or was one. I recently asked him why he did not get 12-inch carbons. His objection was that by using a 12-inch carbon the resistance would be such that it would injure the light; his son is also an operator and claims the same thing, whereas I believe they are in error. Unless you are working right up to the capacity of your carbons, a thing which it is not advisable to do, the resistance of 12 inches of cored carbon is negligible. By actual experiment, made by the editor, the insertion of a 12-inch S^ cored carbon in a circuit carrying 35 amperes only caused a drop of a little less than one ampere, so while, of course, this amount is something, still it is not worth bothering with in practical affairs. Your employer and his son are mistaken. A great many operators believe there is an enormous amount of resistance in 12 inches of carbon, but, as a matter of fact, there is not, unless, as I say. you are working right up to capacity, which would with a H carbon be about 45 amperes. But aside from this the use of 12-inch carbon doesn't mean you would have 12 inches of the carbon actually in circuit. You could not have much more than 6 inches, unless you had a very short lower carbon and a correspondingly long upper one, a condition which is not the best. With modern lamps there is no use in usinj^ 6-iiich carbons on top; they are built to take a 12-inch carbon and the use of tiie 12-inch carbon is more economical and much less bother. Operators Attention. At last, after a long hunt, I have found what seems to be a really practical work on electricity which fits the need of the moving picture operator. I have been looking for this kind of a work for lo, these many moons. It has been extremely difficult to find and the credit for its discovery lies with W. H. Rosenblum, Chicago. Illinois, who very kindly sent a copy to the editor. The book is entitled, "Lessons in Practical Electricity," by Swoope, fourteenth edition, revised, and up-to-date. After carefully examining this work I can heartily recommend the same -to operators. I believe this book, in conjunction with the Handbook, will supply every need of the moving picture operator, at least so far as the -electrical end of things goes. Mr. Swoope's work is such that any man -can readily grasp and understand it. It gives the rules, and other things •which the operator ought to know, in plain understandable language the part dealing with generators is particularly excellent. This book contains 502 pages of text matter and illustrations, aside from the index, etc It •is well bound in cloth; the price is $2. Until other arrangenaents are Operators Are you perfectly sadi with the results you get < the screen? The new second edition of the MOTION PICTURE HANDBOOK FOR MANAGE] AND OPERATORS By F. H. Richardson 420 PmgeB IlluttrateJ will b« the standard textbook on the subject for vama^ Address all orders and rcmittancM t* MOVINO PICTURE WORLD.