The Bioscope (May-June 1912)

The Bioscope, June 13, 1912. 813 HELP IN TROUBLE. FOR PROPRIETORS, MANAGERS, AND OPERATORS. “'W. BP.” seeks information regarding acting for the cinematograph, and asks if special training is necessary, whether the work is regular, and the pay higher for dangerous work ; also, if any firm of producers would consider an application from a “rank outsider ’’$ We think you would suffer great disillusionment, “W. P.,” were you to seriously consider entering the ranks of would-be cinematugraph actors. In the first place, your chance of obtaining a “shop” would be very remote. Apart from the fact that cinematograph stock companies are almost an unknown quantity in England, there are hundreds of experienced artists endeavouring to procure employment as cinematograph actors or actresses, and, therefore, an application from a “rank outsider,” as you put it, would be comparatively hopeless. The work is by no means regular, except as a member of a stock company, and we are quite unable to answer your query as to whether the pay is higher for “dangerous work.’”’ Altogether, “W. P.,” we can only echo Punch’s advice—“ Don't!” * * * “G. W. W.” wishes to know how he can become a member of the N.A.C.O. Your best course, “G. W. W.,” would be to ly to the Hon. Secretary, N.A.C.O., 1, Broad urt Chambers, Bow Street, W.C., who will forward all particulars. We might mention, however, that you will be required to prove your ability as an operator, and, if you are successful in passing the Board’s examination, you will receive the necessary certificate. Your second question will be answered in our next issue. : * * Jim wishes to know if acetylene gas can be used, successfully, for projecting pictures, and, if not, what would we recommend, as he anticipates equipping a theatre in a country town, where no electricity is available: a * We are sorry to have to inform you, Jim, that acetylene as an illuminant for anything but pictures under 4 ft. in diameter is out of the question, ** The Modern Bioscepe Operator” is the ONLY textbeek dealing with Bioscope Oporating. Essentially pracGeal, it is a work which is of the utmost value. Price 3s. 6d. Post Free, 3s. 9d. Ganes, Limited, 85, Shaftes bary Avenue, W. Google so you would be. well advised to dismiss all idea of using this gas. There are two things open to you —limelight, and an electric generating plant. If you have no opposition, or if electric projection is | unknown in the town, you might use the former, in which case a £10 note would cover the cost of * your jet, regulators, and the details of a limelight : equipment. On the other nand, an electric gener: ator, to be run from either town gas, oil, or petrol, * could be obtained from £80 upwards, depending, of course, upon its size. Such a plant, we venture to think, would be far more satisfactory to you: than using limelight, and certainly the running. cost would be lower. * * * “F. GW.” wishes to know how to ascertain the voltage across the terminals of his arc lamp. He says: ‘I am using 200 volts, and I divide 200, by 25 to get the resistance required for obtaining 25 amperes current. This is & ohms, the required resistance, but that does not tell me what I have reduced 200 volts to. I know the full pressure is still in the mains, but I wish to know what pressure is still at the lamp terminals.” The only satisfactory way, “F.G. W.,” of ascertaining the pressure across the terminals of an arc lamp is by means of a volt meter. Certainly, by Ohm's law, pressure can be ascertained when twa other factors—current and resistance—are known. Now, in the case of an arc lamp, this latter is a very variable quantity. As a matter of fact, the resistance varies continually, as the carbons burn away, and are subsequently fed. When burning, normally, a voltmeter bridged across the terminals. will indicate a pressure somewhere between 40 and’ 50 volts, most probably nearer the former. However, knowing the variability of the arc lamp resistance, we usually take an average of 45 volts across the terminals of the arc, and from this ascertain the resistance. Now, you are slightly’ wrong in your premises. You say that by dividing 200 by 25 you will get the resistance required for 25 amperes—presumably through the arc lamp connected in series. This is not so. The 8 ohms you obtain is the total resistance that, on a 200. ‘« The Bioseope Electricians’ Handbook,’’ by James W. Barber, A.M.I.E.E., is a concise little work on Bisecope Electricity. Seven full-page wiring diagrams and a large number of smaller illustrations. Price 1s., post free, Ganes, Limited. 85, Shaftesbury Avenue, W.