SCIENCE AND INTENTIONS.

New Zealand Herald, Volume LII, Issue 16020, 11 September 1915, Page 4 (Supplement)

SCIENCE AND INTENTIONS.

RUBBER SHEATHING FOR SHIPS. Tire' loss ;of the Lusitania draws attention once again to the possibilities, of. rubber as a cheating-or lining for the hulls of ships to avert or minimise a catastrophe such ias that' which then j occurred.'.; A good deal of research is understood to Have taken T place more or lees on.these lines, and the. granting of patents for apparently hopeful devices has been mentioned from time to time. Experiments haveSshown conclusively -that' rubber.' is almost invulnerable to explosive attacks, "and the application of the principle to shipping does not seem to present insurmountable difficulty. THE CINEMA IN THE NAVY. ~ [A large. number of H.M.'s ships now | boast of a cinema, including the Colossus, Assistance, Conqueror," Iron Duke, Queen i Elizabeth, Warspite, Queen Mary* Achilles, and Illustrious. -Some-'details of the Achilles' cinematograph are now to hand. Those responsible for its installation—it is understood, the commander is- closely interested—have carried it out in a thorough manner. , They possess a fine projector, which is run-by a motor, and an excellent picture is ' secured." A weekly change of programme is provided,- also i illustrated song slides, which are a popular feature on board-. \ > ' AN ELECTRIC HAMMER. A portable hammer, for use in drilling holes in concrete, brick, or stone, or for removing scales, paint, or rust from tubes or plates has recently been devised which uses a magnetic clutch to obtain the striking* action. The apparatus, consists of a hollow sleeve about which is the.magnet winding; the ends of the sleeve form the poles -of the magnet. -. A . loose plunger operates within the sleeve. The centre of the sleeve is largely cut away, and the .plunger - normally occupies a position spanning this centre opening. By means of a motor .the sleeve is , reciprocated,, thereby .throwing the plunger back __ and forth by means of the "magnetic coupling of the two.; A BIRD 'MYSTERY.. One of the" most carious and interesting of the .•unsolved problems relating to "bird migration, according ,to Mr. W. W. Cooke's recent memoir on. this subject, is connected with. the* chimney swift, more often . called the chimney "swallow," a very common and well-known bird of the Eastern "United States. -After the breeding season the flocks drift slowly south and concentrate in vast numbers on the northern coast' of the Gulf of Mexico. Then they . disappear as completely as if, they hibernated under the water or. in the mud, according to the old belief regarding birds in general. - The last week in March thev appear again on the Gulf coast. "Their hiding place during the intervening five months,' says Mr. Cooke,, "is still the swift's secret." / THICK AND THIN SHELLS. There are several kinds of high explosive shells, which have been designed for various purposes. For instance, there are the; shells the* case of which, is very thin, so i that their capacity for containing sive may be increased. These explodein" stantly at the slightest contact, and are used as mines; or, in other words, they cauee damage not by the impact of their mass but by the fierceness of the explosion. 'Another kind of explosive shell is made by increasing the thickness of■ the steel case and reducing the charge of explosiveThe explosion of this missile is calculated to take place a little after contact. This. type is used ; for the destruction of solid defences, like walls >, earthen.' works, etc., as the thickness of the case and the slowness of explosion permit them to penetrate the fabric before exploding. ,* ~. ONE FOOT ALWAYS FASTER. If will'-take a pavement that -is clear, .s.*.'and 'i .waIJL briskly in . the centre. you will"that before you have gone 50yds you';have, unconsciously veered.very much to one side To make this test accurate you-must "'not maK any "effort to keep "in the centre. If you think of something .else and".'endeavour to walk ;: naturally, you will find that you are hot able to keep going in -_*., straight line. In the same way a person lost in a wide expanse of level country will describe a complete circle as ~he •<» keeps'" walking on < and on. The explanation of this lies, in the propensity : of < one foot ; .to'walk,: faster than the other 'or: toy take a longer stride than the other, 't causing you to veer to one side or the other. -- >F - -,*£**

NEW LIFE-PRESERVER. - The ordinary life-belt, when - placed about the body, prevents drowning, ' bnt in a large number of cases there is little hope for the wearer being saved .unless he is rescued from the water quickly. A new device, however, has been designed in the shape of a life-saving suit, which partially overcomes this, for it* wearer does not come in contact with the water. It consists of a rubberised-canvas suit which protects the entire body. It is fitted with' a pneumatic-belt arrangement beneath the arms, and prevents drowning, for should the used become unconscious, or fall asleep, his head, would be held out of .the water. Pockets on the inside of the suit are provided for the storage of sufficient concentrated food to keep a man alive" for a number of days. Access to these pockets is possible bv withdrawing an arm from one of the sleeves. WATERING TREES. A very ingenious and practical device for assuring the trees on city sidewalks a sufficient supply of water, no matter how dry the season and how hard baked the earth, has recently been put in operation in Strasburg by Mr. Sauer, the city tree inspector. It consists of a tube of iron or lead bent into the form of a ring largo enough to encircle the stem of the tree. The earth is removed so that this ring ay be placed just above the roots, and is then filled,in again, leaving the end of a pipe .connecting with the ring projecting above the surface of the ground. - The top ofiHhe ring is pierced with a large number .of small holes, and a tin cover of shield prevents these from becoming stopped up with earth. By means of a funnel in the protruding end of the pipe any desired amount of water may be supplied to the root* without waste, or los? Ofctime. A further advantage, according to* " Prometheus," is the ventilation thus secured of the earth in the vicinity of the roots. ' THE POWER OP PROJECTILES. F. W. Lanchester, in a recent number of Engineering, gives the following interesting facts in regard to the power of rifle bullets. The kinetic energv of a projectile commonly represents from 10 -per cent, to 30 per cent, of the total energy of the explosive or powder charge by which it is jrojected; the lower figure corresponds to the performance of a smallbore, low-velocity rifle, the latter being that approached under the most favourable conditions by the military or biggame rifle. The British service" rifle with Mark VI ammunition thus has an efficiencv of approximately 28 per* cent.; in the ordinary sportsman's "12-bore" the figure is about 11 per cent. The total energv released on combustion by black powder is the equivalent in round numbers of 500 foot- per pound. The corresponding figure in the case of cordite is half as much again, or approximately 750 foottens per pound: and in general it may be taken that most of the explosives in common use have an energy content between 500 and 1000 foot-tons per pound. In the case of the service rifle the weight of the powder (cordite) is 30gr (0.00431b1, and the bullet 215gr (0.03071b), and the velocity 2050 ft per second. Thus the total energy of the charge is 0.0043 multiplied by 750, equal to 3.2 foot-tons; and the muzzle (kinetic) energy is 2000 footpounds, equal to 0.895 foot-ton; the efficiency, therefore, is 0.895/3.2, equal to 0.28, as already given. It is worthy of remark, en passant, that there is very close accord between the figures applying to the gun and those which obtain in* the gas engine in all such matters as "efficiency heat lost to barrel (cylinder walls), and heat remaining in gases. The agreement is far closer than one would have ventured to expect in view of the great disparity in the conditions. • - " "*j