The Optical Magic Lantern Journal (April 1895)

The Optical Magic Lantern Journal and Photographic Enlarger. 69 form water ; from the bladder they were condensed by an assistant with a hand syringe into a strong rectangular copper gas vessel, from which they came out through a valve into a pipe leading to the nozzle; this pipe was furnished with a stop-cock to turn on the gases when required. The nozzle itself was a capillary tube ; the safety valve was the invention of Dr. Cumming, and was an appliance containing wire gauze and oil, with the object of preventing flame reaching the compressed gas in the copper vessel, even should it get behind the nozzle. All that Clarke has to say about Hare in his book is contained in the following sentence :— “ With respect to the application of hydrogen and oxygen to aid the operations of the blowpipe, when propelled from different reservoirs through different apertures, by means of hydrostatic or other pressure, this contrivance is as old as the time of Lavoisier. The American chemists lay claim to it as their invention, in consequence of experiments made in 1802 by Mr. Robert Hare, junior, Professor of Natural Philosophy in Philadelphia, of which an account appeared in Dr. Bruce’s Mineralogical Journal, and also in the Annales de Chimie. Much about the same time, Dr. Thomson also carried on a series of experiments in the same way ;and we have witnessed similar experiments, for at least a dozen years, during the chemical lectures delivered in the University of Cambridge. The combustion of the diamond was always thus exhibited, and in America this plan is still pursued ; that is to say, the two gases are propelled from different reservoirs and through different apertures.”’ The slippery nature of the statements in the foregoing quotation may be pointed out, for they were admirably calculated to confuse the public mind. He speaks of hydrogen and oxygen “aiding” the action of the blow-pipe, but in Hare’s case they were, after mixing, the active agents of the blow-pipe itself. He speaks of the gases coming out at different apertures, thereby intimating, without asserting, that Hare did not also make a blow-pipe in which the gases came out at a single aperture, which vital fact is kept back from the readers of his book. Having no act of publication to fall back upon to depreciate Hare’s work, he falls back upon a letter written to himself seventeen years later, also upon chemical lectures at Cambridge, which, after all,referred not to a mixed jet, but to one in which the gases came out at separate apertures. Any ordinary person reading the paragraph we have quoted, and not examining original documents, would have thought that Hare had no claim in the matter. Claims to priority must rest, so far as the scientific world at present is concerned, upon the dates of publication ; alleged occurrences in private life are outside the sphere of public investigation or recognition. As to his own invention and its merits, Clarke, after persisting in asserting that by the American plan the gases were propelled through ‘different apertures”—which was not the case—goes on to say :—‘‘ The intensity of the heat is incomparably greater when the gases, after compression, are propelled and burned in a mixed state ’—thereby again implying that Hare did not use them mixed—‘ because the due proportion necessary for forming water is then constantly and equally maintained; whereas an excess, either on the side of the hydrogen or the oxygen, not only tends to diminish the temperature, but if it be much increased on the side of the oxygen, infallibly extinguishes the flame.” Here, however, is what that excellent authority Mr. Lewis Wright has to say on this point in his book on ‘“ Optical Projection,” Longmans, London; 1891; page 51 :—‘‘ The first arrangement employed was to mix pure hydrogen and oxygen, in the proper combiuing proportions, in one vessel, expelling the mixed gas through a minute orifice. It is often stated that this method gives the most brilliant light. This isa total mistake. No light was ever obtained in those days nearly equal to what is obtained now.” Much of Clarke’s book is filled up with irrelevant matter about eruptions at Vesuvius. It also ends as did Hare’s first paper on his invention, with descriptions of a number of experiments with the oxy-hydrogen blow-pipe. Clarke, in The Journal of the Royal Institution, once published :—‘‘ I consider this improvement in the blow-pipe one of the most valuable discoveries for the sciences of chemistry and mineralogy that have yet been made.” To which Hare replied :—‘‘ And thus does he modestly claim to his modification the whole merit of the discovery, for it must be observed, he does not in saying ‘improvement on the blow-pipe ’ allude to the compound blow-pipe invented by me, but to the ordinary blowpipe of the mechanic or meteorologist.’ See Silliman’s Journal for 1820, Vol. 2. Clarke, then, was not the inventor of the oxyhydrogen blow-pipe ; he invented an inferior and highly dangerous form of the instrument, and seems to have done his best to leave English readers to infer that Hare’s blow-pipe did not yield a mixed jet but delivered the gases from separate apertures. Clarke’s blow-pipe was also wrong in theory.