SCIENCE NOTES.

Otago Witness, Issue 2892, 18 August 1909, Page 76

SCIENCE NOTES.

— Order for Radium. —

The largest order for radium ever given has beer? placed by Lord Iyeagh and Sir Ernest Cassel. The quantity ordered is 7£ grammes, rather more than ioz. The price is £30,000, equal to £1,824,000 a pound. The largest amount bought before has been one gramme. The radium is to be presented bj Lord Iveagh and SixErnest Cassel to the new Radium Institute in Ridinghouse street, Portland place, for the foundation of which they provided the funds.

snetrable Air. —

The discovery that air may be made as impenetrable to shots as a plate of armour '■would seem to suggest interesting possibilities. In his curious experiment at Buc, near Versailles, Robert Esnault-Pelterie stood at a considerable distance behind his aeroplane, the propeller of which was going at full speed, and fired a number of dhote art the centre. The whirling column of air BiUsoessfully warded off every bullet. When the propeller was stopped it was found that not only had the <«ntre escaped, but even the blades had not been touched.

—Hard to Kill.—

Some curious experiments have just been made by a student of electricity. He tried a strong electric current in killing sroaches, and they succumbed at the first shock when placed in water as a conductor. Other insects were killed just ac easily, tbttt he n*st with a surprise wJien he tried ifc on a. common house fly. Placed in a ipool of water charged with ail the power from an electric light wire the, fly gave 110 sign of being even troubled by th© current, and the experimenter is endeavouring to find out the reason. The fly took the current which would have killed a dog, oat, or horsa.

—The Earth's Crust.—

For the best essay on the earth's interior, the Unuivereity of Jena, Germany, has just awarded a prize to M. Thiena, whose theory is thus outlined: — The mean density of the earth is known to be more than five times that of water. As the surface rocks have an average density of only 2£ and- water of 1, the interior must have a density x>f about 7.7— that of iron. It is fairly certain, also, that the rigidity ie slightly greater than that of steel. He concludes that the earth's crust is about 930 miles thick, instead of the 30 miles of the common estimate, and that it encloses a very dense and rigid core which he calls the barysphere.

— Problems Yet to be Solved. —

PrLnee Henry of Prussia, the Kaiser's brother, described in a. lecture at Kiel hia trip in the Zeppelin airship. Prince Henry regards the noise of the propellers as a. serious disadvantage, being calculated to betray the approach of the airehip in war time. He described how he took the helm, and satisfied himself that, despite the vast clumsiness of the steering tackle, the huge .vessel answered the helm as easily as a steam pinnace. He regarded the problem. of reaching' a fixed and not too distant point in not too unfavourable weather as solved, but as to the question' whether dirigibles were at present suitable as regular means of communication or could oe employed for purposes of war, that must I ■be regarded sceptically, for air currents, ' head winds, atmosphere disturbances, and the tenuity of the air at great heights yrere difficulties not yet overcome. ,

—Secret Wireless Telegraphy. —

A new no-spark system of wireless telegraphy and telephony has just been invented by Dr Lee d« Forest, and is expected (says Popular Science Sittings) to 1 aiter the entire field of wireless communications. Present systems of wirolees telegraphy send intelligible signals by means of sequences of explosive discharges from Leydsn jars, which on spanning the spark gap create an etheric impuiee detachable by the proper Apparatus. It is known that ai> operator within hailing distance can read any message received, and that secrecy is impossible. The new system relies on a low power, high epeed, continuous wave train, which, according to those in the know, exceeds the spark system in both penetration and range, and is faster in operation. Its signals are occasioned by j instantaneous interruptions, which can be ■ made at the rate of more than 100 a second, instead of the dash and pause ' system in vogue to-day. It i 6 said that secrecj in the sending of wireless messages will be possible by the new system. j

— Wonderful New Photography. —

Remarkable discoveries concerning the (planets and the heavenly bodies are constantly being made through new methods in the scisnee of photography. It has long been known that the camera can detect objects and movements of the heavens which are beyond the reach of the human eye, even with the aid of a telescope. 'A new method of photography by which pictures can be taken without a camera promises to be of especial service in gathering new reoor<3<3 of the skies. It is to Professor liippman, of the Paris University, that ive are indebted for the wonderful Arguseyed plate which requires neither separate Jene uor camera. The surface of the plate 16 covered with tiny lenses, of which there are 15,000 in the square inch, the whole forming a kind of gelatine honeycomb. The plate has merely to be exposed for a certain time, and then it can be covered and treated. The result is a wonderful photograph which is far different from any now known, as the objects stand up in relief as though seen through a stereoscope, and the perspective is not distorted, which is tihe case with the present methods. By the Donmsthorpe process, photographs need no ■longer be taken upon glass or similar transiparent substances. The photographs are (taken upon black- paper. . Prints can be taken from these negatives,, -and also the usual kind, by immersing them in a dye; ithe paper is placed in dose contact, and >vhon pulled off the negative contains *a faithful reproduction in the same colour Bfi the dye used. Thus, a multitude of various coloured photographs can be obtained, irrespective of illumination.

— Simple Ice-making 3fe«v.'/io.—

One of the simplest of the devices for foe-making on a. email ecala is that known. as the Raplin, which has recently been perfected. This machine is constructed on the principle that water will freeze when rapidly evaporated by means of a T«cuum pump and a powerful absorbent

such as sulphurio acid. It is simple in design, contains few integral parts, so that liability to derangement is rendered very remote, andj can be operated by anyone of average intelligence. A carafe of water will freeze in three minutes or a solid pound-block of ice be _ made in about 20 minutes. Vacuamising is effected by means of a hand-wheel, or the machine can be worked by power if desired. The advantage of this handy little machine is that ice can be made anywhere and at any time, irrespective of the prevailing temperature, so that there is no loss arising from melting. Owing to its small dimensions, it can be conveniently stowed in a small space; while the fact that no expensive chemicals for producing the freezing efflacts are required is a distinct characteristic. The cost of manufacture is merely dependent upon the expense of the absorbent, and sulphuric aoid is always readily obtainable and at a low figure. One charge of acid (two quarts) is sufficient for from 50 to 100 freezing operation®, and approximately Sib of solid ice can be made with each pound of acid. No danger need be entertained in regard to the safety of the machine, and so long as the simple instructions are followed failure is impossible. These Tiachtnes have been subjected to severe tests in tropical countries, and their complete success in ssch climes testifies to the soundness- and oractieaoility of the principle adopted in tneir design. — Chambers'c JournaL

Revolution in Tunnelling. —

Like the poor, new ideas for tunnelling through rock and doing away -with drilling and powder a.n3 dangerous blasting are forever with us. Some have shown- merit, but there still remains a. large field for inventive development. The most hopeful departure we (Science Sittings) have encountered is due to aMr Sigafoos. We are told by an expert, Mr Rowland A. Phillips, -who has seen the machine at work on its trial trip, that in every instance the rotary proved its value, and came up to the highest expectations. Mr Sigafoos will guarantee to cut sft an hour, 24hours a oay, in any and -all rock. The machine oomplete, ready for work ; weighs 29 tons, and ite length is slightly in excess of 18ft. This huge frame holds 10 crushing heads, each carried on a 4in horizontal shaft and working on the same principle ac a stamp mill, with the exception that the blows are given with the aid of springe instead of force of gravity. The entire fore part of the machine revolves as it out 6, thus cutting a full, clean bore, all the rubbiah being flushed from the tunnel by means of a 3in stream of • water, carried directly through th-e machine under 401b pressure, and fed through 10 small nozzles, each of which sends a stream beside each, crushing head. Scarcely any timbering will be needed, as this machine cuts the walls as smoothly as dressed marble, instead of shattering them, as is done with powder. Then, too. all powder and fuse are done away -.with, and only a third as many men will be needed. And lastly, but one of extreme importance, the work is accomplished absolutely without the least dancer. Subways, we are told by Mr Bhillips, that formerly took five years to construct can row be run for half the expense in one-tenth the time. The machine ■is being made in different sizes in order to make it adaptable for practically any kind of tunnelling.

—An Ingenious Type of Tin.—

For some time past considerable enterprise has been exercised by those engaged in industries where ths product of the-ir labour has to b& packed in tins in supersetting the old-fashiond hermetically-sealed! vessel. These are extremely dangerous to open, as a slip of the cutter will often produce an ugly and dangerous wound by the flesh coming into contact with the jagged edge of the cut metal. The lever-hd tin overcame this serious disadvantage, but it was far from perfect. Recently, however, a distinct improvement has been effected which overcomes the foregoing defects in a marked degree. The top edge of the tin, instead of being left raw. is properly finished by fake wiring, so that it presents a smooth, clean surface, which may be handled without any fear of a wound being inflicted. The result of the development is that not only i« a much stronger tin produced without any increase in the weight of the metal, but the mouth, being the full circumference an<l having no inside ledge, can be moro easily filled and the contents more completely extracted. This ensures tha*; there will b* no waste. Aeain, a- spring clip-on hardle ii provided. gripping ,the top and bottom edsres of the opened tin. so that it is converted into a mug. In cases whore the vessel is filled with such substances as piint and co forth, and thore is no need to discharge the contents, it can be handled and carried about with as much facility as the ordinary pot. beinfT sealed whenever desired merely by slipping in the lid, which forms an air and liquid tight joint. Or if fh*> tin has bean filled with something which ran be cleanly emptied out, such a* fruit, it will, when empty, prove a ser\icoab!o article, with its haVdv clip-handle, and be available for a large varietj of purposes.

serious. The treatment should, of course, be principaly preventive ; scrupuous ceanliness of the hands, and, indeed, of the entire body, being observed by all those who have to work with lead. The fingernails should receive attention, and the teeth should be cleaned twice daily. Frequent warm baths should be employed. Any tendency to constipation should be corrected.