The Optical Magic Lantern Journal (April 1901)

42 The Optical Magic Lantern Journal and Photographic Enlarger. forward in good faith, and with the full belief that it accurately states the case. Twenty years ago the mere fact of a man being selected as one of the Polytechnic staff of lecturers at once placed him in the front rank of his profession, the reason being that the standard of excellence was maintained at a high level, and in this the. directors were assisted by the lecturers themselves, who designed their lectures with care and illustrated them fully by means of numbers of expensively prepared paintings and photographs. Thus, by years of careful and painstaking work, the Polytechnic lecturers made for themselves a little niche in a quiet and unobtrusive ‘corner of the Temple of Fame, which they fondly hoped would be theirs so long as they lived to enjoy it. But it was not to be; others unable to secure the favourable attention of the public by their own unaided endeavours, bedeck themselves in the borrowed plumes of “late of the Royal Polytechnic Institution,” but in many cases the result is identical with that in the fable of the “Ass in the Lion’s Skin.” They have only to raise their voices to expose their deception; in other words, a “lecturer ” of this calibre only opens his mouth to ‘ put his foot in it.” The subject is not a pleasant one, but in the interests of the general public and the Polytechnic lecturers, those who use the words “late of the Royal Polytechnic Institution” without being entitled to do so, should be warned that they are describing themselves falsely, and are guilty of an impudent deception. =O Oi Why ? Oil Lamps. By R. J. MOSS. AKE the first step in lantern illumination, the oil lamp, how many, or rather how few, know why it } burns, or shall I not be more cor rect in saying, why they get no light, but plenty of smoke ? Without going fully into the details of combustion, I will just mention that petroleum is exceedingly rich in hydrocarbon, and light is nothing more nor less than carbon particles brought to a state of white heat or incandescence by an inflammable gas. Now, if you light’ a petroleum lamp and do not put on the chimney there is more smoke than light. Why? Because there are too many carbon particles and not enough inflammable gas to reduce them to a white heat, consequently, the carbon particles are unconsumed and go off in the form of smoke. But why the chimney? Simply to induce a current of air, largely composed of oxygen, to increase the amount in volume of combustible gas and make it sufficient, not only to render the carbon particles incandescent or light-giving, but to absolutely consume them ; therefore when the combustion is perfect there is and can be no smoke. , But, says one, would it not be as well to put the chimney directly over the flame and let the oxygen come freely without all those bothering cones and sieves which are so much trouble to get at and so impossible to clean properly in & lantern lamp? Well, why do you. break up coal before putting it on a fire if you want it to burn properly and give a good blaze, or why put on big lumps if you want it to keep ina long time and burn slowly? Just for exactly the same reason are the perforations, cones and grids put into a petroleum burner, viz., to ensure quick, proper and perfect combustion, by breaking up the fuel into small particles. If the air were to be sucked up in a body there would be plenty of heat, any amount of unsteadiness and clouds of smoke, but little light ; by dividing or splitting up the oxygen at the proper distance from the flame and directing it by means of the cone so as to strike the flame at the most advantageous point, together with carefully regulating the length and size of the chimney, which sucks or draws up the air, perfect combustion is secured with absence of smoke and a pure white light. I do not propose going into the why or the wherefore of the building up of a lamp because this is beyond the subject, and further, the lamps are provided with all these features carefully worked out, more or less. Now, please just look back and see what I have written means; first, the holes, sieves, cone and chimney are just arranged so as to give best results, and there is no room for alteration in the slightest degree if best results are to be obtained. We are always told to keep our lamps and burners scrupulously clean, trim the wick perfectly straight, etc., but we are not told why. We are not told that a lining of soot in the chimney, a coating of dirt, dust and oil, assorted, on the cone, a further collection. of the same with the addition of sundry pieces of charred wick snugly nestling on the grid or sieve, all tend to reduce the proper and necessary supply of oxygen, and, therefore, by rendering