International Review of Educational Cinematography (Jan-Dec 1931)

Record Details:

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— 1002 — enabled one to observe and manipulate organisms which were outside the area of the picture. To the eye the illumination appeared extremely brilliant, but the results were never satisfactory as in spite of the use of very rapid film-stock the exposure was far from sufficient. The obvious desideratum was a more brilliant illuminant, but further experiments with this type of microscope were never made, chiefly because my early experiences of illuminants sufficiently powerful to operate it convinced me that to conceal them in a closed lantern was courting disaster ; and by the time my lights became safe and reliable I had replaced it with other contrivances. I think, however, that the closed lantern microscope would be quite practicable and it has several advantages. Vibration is reduced to a minimum owing to the disassociation of the microscope and camera, also one obtains upon the film an image very conveniently placed for observation. In my present types of film-observing microscopes the view-point is oblique, and, until one gets used to it, rather perplexing. Having broached the question of lights I will add a few remarks upon this subject. For some types of work requiring low amplification oxy-coalgas will suffice, using a small jet and replacing the lime by a Thorium pastille; but for moderately high power work a greater actinic value is required. Oxy-acetylene admirable satisfies ordinary requirements. My first generator, used with the enclosed lantern gave very low pressure. To remedy this I sealed up a large carbide container, furnished with an inlet and outlet system of tubes. This was filled with water and as it emptied drew gas from the low-pressure generator. When the container was full, acetylene under sufficient pressure for an oxy jet was obtained by running water into it from the tap. Several quite useful shots were made with this device, but its habit of notifying lack of gas by substituting a jet of water in the lamp was prejudicial to concentration one one's subject. After a time it became increasingly difficult to manage, and persistently fired back in the jet with a disconcerting pop and prompt disintegration of the pastille. I finally tracked down the cause — a leak in the tube between the generator and the container. I had, in fact, been compressing a mixture of acetylene and air, and I owe my life the fact that Mr. Fallot, who made the lamp, had shown a sympathetic regard for congenital idiots by placing a wire gauze safety device in the base of his blowpipe. I now employ dissolved acetylene in cylinders, and, used in this form, the gas in extremely convenient, safe, cleanly, and instantly available when required. In purity the dissolved gas is far superior to that prepared with a generator, a point of importance as the tiny jet of the burner clogs easily with any impurity. Presuming that one is working with the ordinary type of Oxy-Acetylene-thorium jet it will soon de found that the system possesses two drawbacks. Fortunately these can be eliminated. In the first place when starting up the jet, and before the correct quota of oxygen has been admitted,