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Messrs. Dewar and Fleming, who, it is true, extended their examination to various metals, alloys, and non-metals. But the execution of these labours meets with no difficulty; for the method of getting large quantities of liquefied gases is now generally known."

Let us see what Professor Olszewski said in that paper entitled "Transvasement de l'oxygène liquide," June 1890.

"A flask of wrought iron, 5 litres in capacity (such as is used to hold liquid carbon dioxide), containing oxygen under a pressure of 80 atm., is joined by a narrow copper tube to the upper end of a steel cylinder tested at a pressure of 200 atm. This cylinder, having a capacity of 30-100 cubic centim., according to the quantity of oxygen which we wish to liquefy at a time, is immersed in liquid ethylene, of which the temperature may easily be lowered to 140° C. by means of an air-pump. The lower end of the cylinder is joined by a narrow copper tube to a little stopcock, through which the oxygen, liquefied in the cylinder, can be poured down into an open glass vessel kept cool by the surrounding air."

In other words, replace the glass tube in my apparatus of 1884 by a small steel cylinder and attach to its lower end a narrow copper tube with a stopcock, and the Olszewski apparatus of 1890 would result. As a matter of fact Pictet had used the same principle in the year 1878, and to take credit for originality in repeating his device seems a little absurd. Now on the 11th of June, 1886, I delivered a lecture on "Recent Researches on Meteorites," and the report in the' Proceedings. of the Royal Institution' contains a sectional drawing of an apparatus (reproduced on the other page) solely constructed of copper, together with a valve for drawing off liquid oxygen, entirely different in type from the plan Olszewski adopted in 1890. I may mention that the plan of the apparatus was reproduced immediately after the delivery of the lecture both in England and America. The section is confined to the refrigerator, all the accessories of liquefied and compressed gas-bottles, compression and exhaust gauges, &c. having been omitted. From this plan of the refrigerator, any person so desiring could increase its capacity so as to work on a larger scale. The drawing shows the apparatus arranged for the special experiment of ejecting liquid oxygen into a vacuum-chamber, but it is clear the apparatus discharged more easily into an ordinary open vessel. It is the form of apparatus that is in dispute, not the result of any particular experiment. The special object for which it was in use in this lecture was to cool a piece of Meteorite before insertion into an Electric


Furnace. The following extract from the lecture will explain how the subject was introduced :

"Meteorites, no doubt, have an exceedingly low temperature before they enter the earth's atmosphere, and the question had been raised as to what chemical reactions could take place under such conditions. It resulted from Professor Dewar's investigations that at a temperature of about -130° C. liquid oxygen had no chemical action upon hydrogen, potassium, sodium, phosphorus, hydriodic acid, or sulphydric acid. It would appear, therefore, that as the absolute zero is approached even the strongest chemical affinities are inactive.

"The lecturer exhibited at work the apparatus by which he had recently succeeded in solidifying oxygen. The apparatus is illustrated in the accompanying diagram [p. 301], where a copper tube is seen passing through a vessel kept constantly full of ether and solid carbonic acid; ethylene is sent through this tube, and is liquefied by the intense cold; it is then conveyed by the tube, through an indiarubber stopper, into the lower vessel; the outer one is filled with ether and solid carbonic acid. A continuous copper tube about 45 feet long, conveying oxygen, passes through the outer vessel, and then through that containing the liquid ethylene; the latter evaporates through the space between the two vessels, and thus intense cold is produced, whereby oxygen is liquefied in the tube to the extent occasionally of 22 cubic centimetres at one time. The temperature at which this is effected is about -130° C., at a pressure of 75 atmospheres, but less pressure will suffice. When the oxygen is known to be liquid, by means of a gauge near the oxygen inlet, the valve A is opened, and the liquid oxygen rushes into a vacuum in the central glass tube below; some liquid ethylene at the bottom of the next tube, outwards, is also caused to evaporate into a vacuum at the same moment, and instantly some of the liquid oxygen in the central tube becomes solid, owing to the intense cold of the double evaporation. The outer glass vessel serves to keep moisture from settling on the sides of the ethylene tube. By means of the electric lantern and a lens, an image of this part of the apparatus was projected upon the screen, this being the first time that the experiment had been shown on a large scale in public.

"Performing this experiment the temperature reached was a little below 200° C., that is only 50° or 70° above the

*The white material taken for solid oxygen in 1886 was due to gaseous impurity.

absolute zero of temperature, and in the experiment about 5 lbs. of solid ethylene were employed."

This I declare to be the first apparatus (Pictet's excluded) made wholly of metal, being an arrangement of copper coils in which liquid oxygen was made and decanted or transferred from the vessel in which it was liquefied to another by means of a valve and thereby rendered of use as a cooling agent. In support of this assertion I call as a witness Professor Charles Olszewski himself, who states in the Philosophical Magazine, February 1895, p. 189:--" In 1883, and for several years following, I liquefied the gases in a strong glass tube." There is no suggestion made that a steel cylinder and valve was used by Olszewski till the year 1890, whereas four years in advance I had used a much safer and better form of apparatus. Have I ever suggested that Professor Olszewski was anticipated, or attempted to raise any question of priority? With regard to another case of priority that is claimed, I find that MM. Charles Olszewski and Auguste Witkowski, Membres Correspondants, présentent leur mémoire "Propriétés optiques de l'oxygène liquide," on the 3rd of October 1892, and, on referring to the paper, it is dated the 15th July 1892, and the following footnote is added:

"Avant la publication de notre communication MM. Liveing et Dewar ont fait connaître (Phil. Mag. août 1892) les résultats de leurs recherches sur la réfraction des gaz liquéfiés."

But Professor Olszewski is not satisfied by a reference to published papers, he includes unpublished ones as well, in order to include the study of chemical action at low temperatures as having been originated by him. The following extracts from a well-known Continental Journal of what I had done in 1885 may induce him to produce his priority claim in a definite shape. I challenge him to produce any reference to antecedent work in this subject.

Extract from Moniteur Scientifique, vol. xv. (1885), p. 1134:

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"Sur les Solutions d'Ozone et l'action chimique de l'Oxygène liquide. Par Professor Dewar.

"Dans cette communication, le professeur a donné la description de l'appareil et de la méthode dont il s'est servi pour liquéfier les gaz tels que l'oxygène, et après avoir discuté les conditions requises pour le succès de la conversion des gaz dits permanents en liquides, il a rendu compte de plusieurs expériences faites avec l'oxygène liquide. A-130°


l'oxygène perd les caractères actifs possédés par cet élément dans l'état gazeux; il est sans action sur le phosphore, le sodium, le potassium, l'hydrogène sulfuré solide et l'acide hydriodique solide. D'autres substances paraissent éprouver des changements semblables aux très basses températures. Ainsi l'éthylène liquide et le brome solide peuvent être mis en contact sans produire aucune action, tandis que l'éthylène gazeux et le brome liquide s'unissent directement aux températures ordinaires.

"Hautefeuille et Chapuis, en soumettant un mélange d'anhydride carbonique et d'ozone à une grande pression, ont obtenu un liquide bleu dont la couleur est dûe à l'ozone. Si l'air ozonisé passe dans du disulphide de carbone à — 100°, le liquide prend une couleur bleue qui disparaît quand on laisse éléver la température, et, à un certain degré, une décomposition d'où résulte une production de soufre. Le meilleur dissolvant de l'ozone est un mélange de tétrafluoride de silicum et de pétrole de Russie. Ces solutions d'ozone sont sans action sur le mercure ou l'argent métalliques."

Prof. Olszewski says:-"The experiments of Prof. Dewar are merely the repetition and confirmation of these researches." Reviewing the work I have been engaged upon during the last few years, either by myself or in consort with Profs. Liveing or Fleming, the following subjects have been taken in hand and so far developed with regard to the properties of matter at low temperatures :

Construction of Apparatus for the production of Liquid Air and other Gases in quantity-High Vacua-Vacuum Vessels for Storage and Manipulation of Liquid GasesCooling by Sponge of Liquid Air-Solid Air-Radiation at Low Temperatures-Thermal Transparency-Refractive Indices-Spectroscopy-Electric Conductivity-Thermo-Electric Properties-Latent and Specific Heats-CapillarityChemical Action-Magnetic Properties-Breaking-Stress of Metals-Solid Matter and Argon in Liquid Air-Phosphorescence and Photographic Action-Liquefaction of Hydrogen, &c. With the exception of the determination of the refractive indices of liquid oxygen my work has had nothing in common with that of Prof. Olszewski.

Now Prof. Olszewski says he has anticipated all this pioneering work. On referring to his list of papers given in the Philosophical Magazine for last month, I find that since the year 1890 he has confined his attention to the refractive indices of liquid oxygen and an attempt to corroborate Wroblewski's determination of the critical constants of

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