Now that the unjversity at the openmg of the next college 'year is to begin the manufacture of liquid air, one of the latest discoveiies in science.ali that jan be learued ot the subject will be of iuterost. A loug interview with Prof. Paul Freer, under whose charge the uew machine will be placed, is pnblished in yestedray's Tribune and pro;eeds as f ollows : "Wuat is liquid air, professor?" "Ihe term is self-explauatory. Each word is used in lts sirnplest, oomtnonest rneaning. Liquid air is air re[Juced to the consistency of a liqnid ; air liquifled." ü "What does it look like?" "Water." "Is it blue, red or green?" "It is slightly bluisb, but geuerally speaking, it is said to be colorless, like tlear water. It can be poured, like water; and drunk like water; but I wouldn't adivse you to driuk it. " "Why not?" "It would kill you in a second It's so insentsely cold that it would literally freeze you to death ; its temperature is 312 degrees below zero. ' ' "But if it is so niuch colder than the normal air, how can it be handled iu the air? Wonld it not evapórate almost instantly?" "It evapórales very slowly; it is surronuded by a jacket of its own chemical self, protecyng it in a measure from the hasty evaporatiou in air. This also explains why liquid air, the coldest thing known, burns like a col of lire. It does not burn in the sense that fire burns ; but it produces the same result, that is, it destroys the tissues. ' ' "Then you daré not tonch or banale liqnid air'?' "Oh, yes; if you handle it gentl,y. The jacket of its own chamical self that constantly surrounds it protects the hand form coutact with the intensely cold liquid air. But if you nhould plunge your band violently through the jacket, the fearful cold wou ld destroy the tissues of your flesh and produce the effect we cali a burn. " ■Liquid air is uot absolately new. It bas been known for a hunctred years that all gases are capable of liquefaction ; the only trouble was to find the proper meohanical meaus; and theu, too, heretofore, it was uot possible to condense gases, except in very small quantities. All gases have been reduced to a liquid condition, except hydrogen, aud now the liquid air process will doubtless 'nake it possible to reduce even hydrogen." "Wbat will b'e the commercial uses of liquid áir?" "It is too early to say. It has a remarkable bearing ou mauy cheniical facts, especially on what is known as the chemistry of low temperature. It will make possible processes and reactions heretofore largely theoretioal. " "Has it any bearing on electricity?'B "Yes, a wonderful bearing, and I doubt not great results will eveutaally come here. You see, accordirig to the ehemistry of low teraperature, there is a point where all condnctors ' are of equal efficiency. That is iron is as good as copper, zinc as good as lead, and so on. Witb the aid of hquid air, it will now be possible to determine the physical and chemical values of couduetors, according to an entirely new method; and what the outcoine will be no man at tbis stage eau say. It tnight possibly revolutionize certain processes in applied'electricity. " 'I will read you a paragraph from ïripler's report and ask yon what you think of it, from a scieutifio standpoint. It is as follows : "It is bewilderiug to dream of the possibilities of a source of power that costs nothing. Think of the oceau greyhound unencumbered with coalbunkers, and sweltering boilers, and smoketstacks, inaking her power as she sails, frorn the tree sea air arouuct Der ! ïhink of the boilerless locomotivo running without a flie-box or firemau, 01 without need of water tanks or coal chutes, gathering from the air as it passes the power which turns its driving wheels! With costless power, think how travel aod freight rates must fall, briüging bread and meat more cheaply to our tables aud cheaply manufactured clothiug more cheaply to our backs. Thiuk of the possibilities of areial navagtion with power which requires no heavy machiuery, 110 storage-batteries, no coal - but I will take up these possibilities later." "I think this is fanciful," said the porfeossor, "for the reason that liquid air, to be commercially possible, :ts it looks to me at this stage, would have to be couflned to sources that are essentially free and natural, as water power. If, on the other hand, you have to uso coal to produce the power to liquefy air, the cost would outweigh the results. " "You notice says that he can make 10 gallons of liquified air froin three initial gallons, and go on prorlucing liquid air from liquid air, after the fashion of perpetual motion?" "It is a physical impossibility. According to this, a machine of this character starting with three, could duce au unlimited amount of the air, if allowed to -ork steadily, vvhich conld be done, because 110 extraneona energy would be required. It would then only be a question of time before all the air in existence could be liqnefied. ïhis reduction to an absurdity shows the fallacy of the claim." The machine wbicfa will be placed in the university through the kindness of Prof. Brush, the great electrician, is ruanxifactured by Linde in Germauy. Said the professor in answer to the qnestiou : "Is it a very complicated machine?" "No, it is not. " "Then why does it take so long to install one?" "There are, so far as I know, only two men who advertise liquid air machines. One is Tripler of New York, who professes te be the discoverer of' liqnid air; the other is Linde, of Berlín. But the New 'York man will uot deliver any machines; at any rate, be is uot prepare to deliver them ; so we will get one of Linde. The price is about 81,200. The machine weighs about 2,000 ponnds. It is really a simple piece oí machinery. lts walls are tested to resist a pressure of 200 atmospliéres. " "ís Tripler really the inventor of the liquid air machine?" "I am not prepared to say. If Tripler discovered liquid air, or made the first liqnid air machine, he must have been very secretive. I bave in my study a Germán scientiflc magazine printed almost four years ago, in which Liode's discovery and his machine are described at length ; and there is a diagram showing the essential feature of the machine. H&wever, as I say, the scientific wond will take no part in this matter, especially at this time We are more concerned with liquid air, itself, than in any dispute between inventors of machines. I wish, however, you would say a word for Linde. An eastern magazine, which recently had a long article about liqnid air, gives all tho credit to Tripler. Linde's name is not even meutioned. " "Linde bas au international reputation. I never heard of Tripler bef ore. Linde is a wonderfnl rnatnematician and a chemist. "