NOTES ON SCIENCE, MECHANICAL INVENTIONS ETC.

New Zealand Herald, Volume XXXI, Issue 9401, 6 January 1894, Page 4 (Supplement)

NOTES ON SCIENCE, MECHANICAL INVENTIONS ETC.

A'' DEFINITION OF ELECTRICITY. S T Prof. Galileo Feraris, the genial Italian scientist), whose name fa well known to all electricians, was .recently asked by a young lady what electricity was, bat, anlike most others when asked that question,- he vantared to answer it, and according :to Cosmos, wrote in French in her* autograph* book the following, of which we venture to give a translation, even though the English language hardly does justice to the original in French :—" Maxwell has demonstrated that luminous vibrations can be nothing else than ■ periodic variations of electromagnetic forces.. Hertz, in proving ,by experiments that eleotro-magnetiooacillations are propagated like light, has given an experimental basis to the theory of Maxwell. _ This gave birth to the idea that , the luminiferous ether and the seat of electric and magnetic forces are one and the same thing. This being established, I can now, my dear young lady, reply to * the question that you put to met What is electricity? Ib is nob only the formidable agent which now and then shatters and > tears the atmosphere, terrifying you with the crash of its thunder, but it is also the life-giving agent which sends from heaven to earth, with the light and the heat, the magic of colours and the breath of life. Ib is that which makes your heart beat to tue palpitations of the outside world, ib is that which has the power to transmit to your soul the enchantment of a look and the grace of a smile."—Electrical World. , HARDENING ALUMINUM. The hardness which aluminum is said, to ' lack can, according to a new process, be imparted to it by the addition of chromium. Of course, certain precautions have ,to be taken bo alloy the two metals, owing to the difference in their fusing-points. If electrolysis is' employed for this purpose, one or another of the known methods can be used, and the alumina, salts of alumina, cryolite, etc., treated direct with a determined quantity of granulated chromium, or chromium in any other suitable condition, or with its salts or oxides.

THE PROCESS OF LIQUEFYING OXYGEN. In the course of an interesting interview with arepresentativeof the Westminster Budget Professor Dewar describes the process of liquefying oxygen in the following terms : — Into the outer chamber of a double compressor I introduce, through a pipe, liquid nitrous oxide gas, under a 'pressure of about 1400 pounds to the square inch. I then allow it to evaporate rapidly, and thus obtain a temperature around the inner chamber of - 90° C. -130° F.) Into this cooled inner chamber I introduce liquid ethylene, which is a gas at ordinary temperatures, under a pressure of 1800 pounds to the square inch. When the inner chamber is full of ethylene its rapid evaporation under exhaustion reduces the temperature to-145° C. (229° F.) Running through this inner chamber is a tube containing oxygen gas under a pressure of 760 pounds to the square inch. The 'critical.point' of oxygon gas—that is, the point above which no amount of pressure will reduce it to a liquid, is -115° C., but this pressure at the temperature of -145° C. is amply sufficient to cause it to liquefy rapidly. In drawing off the liquid under this pressure, I lose nine- tenths of it by evaporation, and I have not yet seen how to diminish that loss. Every pint of it which I collect therefore represents ten pints manufactured. In all, I have thus far collected and used about fifty gallons, and the cost of machinery and experiments, very generously met by subscription among members of the Royal Institution and others, has been about £5000 sterling."

THE ABSOLUTE ZERO. "As we approach the zero point of absolute temperature," says Professor Dewar, "we seem to be nearing what I only call the death of matter. Pure metals undergo molecular changes, which cannot yet be defined, but which entirely alter their characteristics as we know them. Tensile strength, electrical resistance—in fact, the whole character of the metal. At 200° F., strange to say, iron becomes as good an electrical conductor as copper, 'while It* is more than probable that at the t zero of absolute temperature, if nob before, the elec-trical-resistance of all metals reaches its zero point." That its discovery will be a key to many unsolved ' problems in electricity, in matter, in light, and the great inscrutable mystery of life itself, is nob to be doubted. A key to the vast storehouse of future electrical inventions has been obtained in this liquefied oxygen. . Who knows what the storehouse will' contain when the door is opened ?

TIDEWATER GLACIERS. Mr. H. F. Reed, in his public lecture on " Glacier Bay, Alaska," says thab Glacier Bay is the most accessible region in which to see large tidewater glaciers. There are eight glaciers which discharge bsrgs. into its waters. The largest of these is Muir Glacier, which drains an area of about 8000 square miles. Ib is moving with a maximum velocity of about seven feet a day, and is continually discharging, large icebergs from its end. its fluctuations have been great within recent times. . One or two hundred years ago ib extended, in common with the other glaciers of the bay, twenty miles below its present endiug, and not long before that the glaciers were so small that valleys now barren and bleak were occupied by large forests.—American Journal of Science.

WHERE METEORS COMK FROM.

If, about 200 years ago, a witness had stated that he had seen a witch riding through the air on a broomstick, he would have been believed; but if 'he had stated that he had heard a loud explosion, and found a large hole in the ground, and, upon thrusting his hand in, had touched a stone that was warm, his veracity would have been doubted. Meteors must have fallen in olden times, bub ibis only in later days that these cases have been reported. Until 1794 it was the belief that meteors were visitations from God. The beat known meteor is one of 1874, which fell in the town of Wolverhampton. A butcher saw a hole in the ground, and an examination showed the ground to be warm, and a meteor was finally unearthed which weighed about 700 pounds. Being polished, ib resembles solid iron, and is rtow stored in the British Museum. In falling, meteors start from above the atmosphere, where there is little resistance, and come down with a velocity 20 times greater than thab of a bullet. Coming in contact with the atmosphere, great heat is generated, and the meteor is usually broken in 'pieces. The most common meteors are stones, and cannot be found because they . resemble stones on the earth's surface. In Siberia and South America the most are found. Where they come from has caused much discussion. One theory is that meteors originally came from the earth, and were due to stupendous volcanic eruptions of ages gone, when the meteors were thrown beyond the attraction of the. earth, and accordingly sent revolving around the sun. When the earth in its orbit comes near one of these" wandering meteors it Is attracted, and plunges into the earth. Any stone thrown ab the rate of .six miles a second would not return to the earth ,-Again, but would be thrown outside of its attractive power.—Pearson's Weekly. j ; ■