SCIENCE NOTES

New Zealand Times, Volume XXXVII, Issue 8338, 25 January 1913, Page 9

SCIENCE NOTES

"While bright-eyed Science watches round."

“Engineering,” reviewing the report of the Advisory Committee for Aeronautics for the past year, points out that researches render it more and more clear that the laws which govern water currents arc also applicable to air currents. While a good steering ship on the sea never requires more than 2) do", to 5 deg. at the helm to keep her steady, and the ship should never bo more than U deg. from her course, an airship may deviate 30 deg. That a Whitehead ‘torpedo will nm 800 yards on. a straight course without alteration of tho helm is largely duo to tho tailfins, placed as far aft as possible. When the helm of a ship is displaced, the question is whether the centre of pressure is in front or behind the line of motion of the centre of gravity; in tho former case the pressure will tend to increase the swing; in the latter it will reduce it; and the latter tendency will bo supported by placing the fins far apart.

To judge by their behaviour, airships of the Lebauily type belong to the former category. In sea ships the column of water” from the propellers produces a direct thrust on the rudder; in airships the rudders can rarely be, placed in the wake of the propellers, owing to structural difficulties, and the rudder thus depends entirely on the streamlines of the air passing the envelope for the thrust normal to its surface to produce a steering effect. The tail fins direct the stream-lines on to the rudder, and tho steering rudders should be directly behind tho fins; this is so m the Zeppelin ships, and probably accounts for their superior steadiness. To ensure manoeuvring powers, weights should Hi kept as near as possible to tho centre of gravity (in order to reduco the energy stored up during tho angular motion), the helm should bo small, and there should bo means 01 instantly ascertaining tho starting, stopping, and roughly also the velocity of a “swing.”

As regards the resistance of airship models, continues •‘Engineering,” visual and photographic studies show that the flow of air in the tail region, even of an elongated model, is very slow, and that, in fact, a length of 0.8 of the diameter can bo taken off from the tip of the tail (when twice as long as the maximum diameter) without affecting the head resistance. The tail might certainly be rounded off, therefore, and lifting power be gained thereby. From the point of view of total balloon resistance alone a fineness ratio (length to maximum diameter) of 6} to 1 will be most efficient; taking also into account the other resistances of tno completed ship, the gas-bag resistance of which would be about two-thirds of the whole, the fineness ratio should bo 5i to 1. From such it is estimated that a balloon of specific form, 40 feet m diameter, travelling at 40 miles per hour, encounters a resistance of 3201 b.

Mr W. F. Denning, F.R.A.S., of Bristol, writes to the ‘"Westminster Gazette” respecting an aviquake and strange noises heard in England on November 19th last: “No doubt the phenomena alluded to had their origin in meteoric explosion. I hav© investigated several instances of similar kind, and the conclusion has been irresistible that they were induced by fireballs undergoing disintegration high in the atmosphere. And in the recent case this explanation is rendered highly probable from the fact that the period from November 19th to 23rd is well known astronomically for its abundance of detonating fireballs. Messrs Greg and Herschel attributed a special significance to the period named, and their deductions have been fully corroborated by later experiences. “There were large meteoric fireballs in 1861, November 19th; 1864, November 20th; 1860, November 21st; and in 1877, November 20th and 2rd, two splendid detonating meteors were seen. The latter, according to LieutenantColonod Tupman, must have produced an explosion more than 100 times as loud as a peal of thunder! Largo meteors were also aeon in 1899, November 19th: 1901, November 23rd; 1903, November 18th; 1910, November 20th; and in other years on similar dates, and they have chiefly been Tau ridsthat is to say, their luminous flights have been directed from the constellation Taurus.

“I observed a well-defined shower of these meteors in 1876,: November 20th, and have witnessed it in many subsequent years. Every ■■November near the end of the third week of the month, there are largo meteors, but they vary in numbers, and at some returns are scarcely seen at all owing to cloudy weather or moonlight.” Mr Charles Tellier, the French inventor of the cold-storage process, is a genius who has devoted his life to perfecting inventions which have greatly helped mankind in general, hut resulted in very little benefit to himself. M. Tellier, when a young man (he is now 84 years of age) invented a method of freezing foodstuffs by means of chemicals, and he spent twenty years perfecting the process. ' It was in 1873 that the French Academy of Science first recognised the value of his labours in a flattering report. In 1876 M. Tellier built the Frigorifique, the first ship specially equipped for keeping the temperature below freezing in the holds, even when crossing the equatoi This ship loft Rouen on August 23rd, 1876, for La Plata, with a cargo of frozen French meat, Which was delivered in excellent condition after a voyage of 100 days. Since that day cold storage has progressed rapidly, ami huge fortunes have been amassed, but the inventor was found recently to be living in Paris in a state of penury. When his condition was made "known, a number of bequests were at once offered. The Argentine Republic sent him £IOOO, and Uruguay £4OO, and the International Cold Storage Association has opened a subscription list for his benefit.