The Optical Magic Lantern Journal (August 1900)

The Optical Magic Lantern Journal and Photographic Enlarger. Not long ago I was speaking to the inventor of a generator specially constructed with one idea in view, and particularly suited for a certain class of work; but which did not compare favourably in the matter of light with another apparatus. He naturally could not see why it did not, or, at least, why it could not be made to; and I had considerable difficulty in convincing him that the very construction which resulted in a brighter light would, if applied to his system, negative the advantages it really did possess. For the sake of simplicity, I will classify the wants of generator users under the following heads :— 1. Low initial cost. 2. Small size. 3. Light weight. 4, Simplicity of charging and emptying. 5. Small quantity of water. 6. To be able to turn lights out without waste of gas. 7. Effective working without restrictions. 8. Steady light. 9. Most brilliant light. 10. Quick recharging during use if required. 11. Indication as to how fast the charge is being used, and how much longer it is likely to last. * 12. Most effective working, combining arrangements for cooling, drying, and purifying the gas, so that there will be no smell or risk of burners going wrong and flames losing brilliancy, even during a three hours’ exhibition. Before going further, I would interpolate a truism generally recognised in the business world, viz., that you cannot get something for nothing; if you save trouble you pay an equivalent in cash, if you get increased light it costs both in money and trouble, if you sacrifice necessary size you also Sacrifice efficiency, and if you buy a cheap machine you cannot have the advantages that a more skilfully designed, expensively constructed and better built generator will ensure. I scarcely know which road to take, in order to make my meaning perfectly clear in the Space at my disposal. Perhaps it will be best for me to roughly summarise the main features of acetylene production in a steady progression, and it will then be a simple matter to compare this with my table of features already given. 1. Acetylene gas is produced by bringing carbide of calcium and water into contact. : 2. Rapid chemical action generates excessive eat. 103 3. Excessive heat decomposes and disintegrates the acetylene, and creates impurities. 4. Impurities not only tend to choke pipes and burners, but also to impair the brilliancy of the flames. 5. The generated gas will not pass through the pipes unless under some pressure. 6. Pressure is produced through more gas being made than the veseel is capable of holding, without compression. 7. In order to produce excess of gas, more carbide must be damped than is actually required to supply gas to the burners. 8. When lights are turned out and active production of gas arrested, this excess of damped carbide will continue to evolve gas. 9. The higher the pressure the greater the ' quantity of damped carbide, and consequent aftermake of gas. 10. A large bulk of carbide will produce greater local heat than a subdivided charge, consequently more impuricies besides a larger excess of damped carbide. 11. A subdivided charge has exactly opposite results, but needs most accurate calculation to balance the automatic control. 12. The light required for lantern and photographic work, must—to be effective—have high actinic properties, and possess more of the violet but less of the yellow rays; this, it must be borne in mind, is in direct contrast to what is best for general lighting, and can only be obtained at a higher pressure and greater consumption of gas, at naturally increased cost. If intending users of acetylene will compare these two tables, they will at once see that, in spite of what generator makers say, no generator does, or can possess every advantage. We will now take them in detail, and then it will not be difficult to decide which of these advantages will be of most service in our particular case. 1. My first customer scans the list, and frankly says, well I can’t help it, I must be ruled by price ; to him I say very good, choose a simple though strong machine without any fancy claims, but do not expect to get as good a light as you will sometimes see, and above all do not be disappointed because you do not, yet under no circumstances try to increase the light by putting weights upon the gas bell; if you do, you will destroy the balance of the machine and probably spell trouble. Be satisfied with fair value for your outlay. 2. My next customer says, oh yes! but I don’t want a great thing like that, I must have