The Pall Mali Budget of London published an interview with Professor James Dewar on what is represented as being "a great scientific discoveiy," that oL making liquid air. Introductory to the interview the article says that "his liqnefactions of permanent gases and the use of vama to preserve great cold mark one of the most important chemical discoveries of the century." It is held by scientists that any gas may be liquefied if the pressure and cold inay be obtained and a vessel of sufficient strength to withstand the great pressures. Of the gases that may bo liqnefied carbonic acid gas has been fouud to be the cheapest and readiest made, and while it has been known for many years that it could be liquified it has generally been so prepared only in small quantities for scientific uses. The use of compressed air as a motive power has presented many difficulties, the principal one being its bnlkiness: henee largo vessels must be used in order to get a sufficient amount of motive power, and it is hard to make these strong enough and at the same tim4 light in weight. As a motive power it is used at a prc% sure of from 600 to 900 pounds. Eut if Professor Dewar has discovered an economical and ready way of liquefying it, it will tend to solve a problem in carrying a motive power in scorage bulk that will be of great benefit to the studente in this line. In the talk with the representativo of The Pall Mali Budget, he says: "Well. I don'tthink there's verymuch to say, because I've told all I have to teil about the matter in my two lectures, bilt I do believe there's a great deal more to be learned about the subject. You see. at present we've got these gases down to 210 degrees below zero, and the lowest possible temperature is 274 degrees below. If we could get some 30 degrees lower down, we impht liquefy hydrogen. Hydrogen has never been liquefied in a free state yet. 'Now, it's a strange thing that air can be made into a hoinogeneous fluid. You would think, as oxygen can be liquefied at - 182 degrees and nitrogen not until - 192 degrees. that as you made the air ooider and colder the oxygen would beconie liquid first and then the nitrogen. I saw tht prediction made in a standard work only the other day. Now, I dare say, you will aak why the oxygen don't come down first." Stepping quickly back to the desk Professor Dewar took up a pencil and began to draw with rapid strokes on the back of a letter. The diagram when it was ftnished looked more like the law of diminishing returns turned up on one side rhan anything else that I am acquainted with. While he drew he rapidly expiained how the mfiuence of atrnospherie pressure on the different volumes of nitrogen and oxygen in air makes them boil almost exactly at the same temperature. As he made each point he frowned a little, drawing up the wrinkles between his eyes. "Now, that, in the old theological days, would have been taken as n providential dispensation. The strange thing is that when liquid air evaporares again they are under the samo pressure, and the nitrogen goes off first, as you would expect. "Ozone can be liquefied by acting on the vapor given off from liquid oxygen by electricity. It is a splendid dark blue color, almost as dark as indigo. Ozone ñas not the sume molecule as oxygen, and the electricity breaks up three twos into two threes. That is the secret of it. The queer thing about liquid ozone is that when it goes back into gas again it explodes. You wouldn't think it, but it is stronger than dynamite as an explosivo. It's simply because the ozona goes back into the molecular form of oxygen so fast. The forcé that comes from the electricity makes it explode without meeting with any outside body. It's a tremendous explosiva, "We have discovered that liquid oxygen acts as a leus. It is so transparent to heat, so to speak, that even at 133 4egrees below zero you can focus heat ■on it from one side and light a piece of paper by it on the other. You know that's just what happens in the earth. The suu's heat gets focussed on to the earth through the lens formed by the vacuüm of space, which is so cold that it hasn't any temperature at all - absoluteiy zero." Professor Dewar gave a lecture on "Liquid Air" at the Royal institution in the presence of the Prince of Wales, tho Duke of York, Lord Salisbury and other notable persons. He showed that by the withdrawal of heat the air is converted into a liquid with total loss of chemical properties, incapable of supporting combustión, or of entering into coittbination even with phosphorus and sodium, while certain physical properties remain. The conversión of oxygen into ozone was also deseribed, and the retention by oxygen of its peculiar optical properties at the lowest temperature was deinonstrated by the very dense and well defined bands of its spectrum. In ordinary conditions oxygen shows no unreasonable thermal absorption, but at low temperature its thermal absorptive power becomes.maniiest.