ELECTRICAL RESEARCH.

New Zealand Herald, Volume LVIII, Issue 17845, 28 July 1921, Page 4

ELECTRICAL RESEARCH.

A DANISH DISCOVERY. TELEPHONE DEVICE FOR AIRCRAFT [fbom ous owv coeeesfondent.] liONDON. June 9. What seems to be the nearest approach to a. solution of the problem of perpetual motion was demonstrated in a lecture before the Institution of Electrical Engineers by two Danish engineers, Mr. Alfred Johnson and Mr. Knud Rahbek, who had been invited to come to London to repeat their experiments. They noticed in 1917 that when an electric potential difference is applied between a solid body consisting of certain badlyconducting materials—e.g., various minerals^—and a conducting body, such as a: metal disc resting on the former body, strong adhesive forces are developed, and these they attribute to electrostatic attraction between the two surfaces. They find that an attraction of several pounds can be obtained between a thick litho- j graphic stone, fitted with an electrode at the back, and a metal disc 2in. in diameter resting thereon, on the application of a potential difference of 440 volts with a very small current. The disc will then lift the stone in a manner exactly similar : to that in which an electro-magnet can be lifted by its armature, and the stone will drop when the current is interrupted - Similar qualities are exhibited by flint, agate, some kinds of slate, and many other minerals and salts, as well as by many organic substances, such as aliimal membranes, skin, gelatine, and bone; bat the experiment cannot be carried out with true • insulators like glass, mica, or hard rubber, because the necessary current will not flow.- What this means in practice is that a few thousand extra miles would make little or no difference in sending a wireless message. The rate of receiving wireless telegraph messages can be speeded up to several hundred words a minute, and so forth. The possibilities of the discovers when fully investigated will un-, doubtedfy lead to fresh advances in many ; branches of commercial electricity. I Mr. William Dubilier, a pioneer of I wireless telephony and telegraphy, who ! has just arrived in this country, explains i some of the latest of wireless developments. He has brought with him an"! apparatus designed to'improve and s im- \ plify wireless telephony from aircraft. He ; explained that up to the present the difficulty of carrying out efficient conversational telephony from aircraft has lain in ! the generating of the current. This is i produced by the operation of a dynamo worked by a propeller which is revolved ! by the air stream forced against it in the flight of the aircraft. Variations in the i power produced, however, result from i variations in the speed at which the i aeroplane* may be flying. The apparatus j in question is designed to correct th ; s de- | feet. It consists of a streamlined I aluminium boss fitted with a single fin. i The fin operates against a strong spring, and is sensitive to wind pressure, its ad- ! justment to the radio set maintaining the | flow of electric current at an even rate, whatever changes in speed may be made j by the airship or aeroplane. j Mr. Dnbilier is convinced that there | w-'TI be entirelv satisfactory wireless tele- j phone communication between London and j New York within the next few vears. ; He has been can-vine ort exneriments on ! land and sea. recentlv with this means of l communication. He described how three davs a week rerrn] a r] v shins in. f*>e : Pacific were with ships in the I .Atlantic by wireless relayed over land lines. "Tlte wireless fplenhoTifl is alreadv wpatK- i"»d in the TTrnfod States." said Mr. "not oni v for oonverc-'+ioTis I ove-'-se-'s hut frvr ordinarv ti~"T>Tc r«]], ip. I land. The te?erjhone .snhs~>- ; >ve'- does pot [ know, in mnnv cases, wh'fber he >s till.-. inv over wires or not. Von ponM V-to j ii-.st same ciTctprn 'p th'c oonntrv Vim • j ♦ *>at it. is s r> rnirintelv fo j the nyrr\-l to *•" Tin ff | I eon cres* ; on ttio f3™~m«Tie are mtln, VoKino 1 „ e nTI( .T ~„,., „;,.„l oe i, I i ttwrV. V<*r the reborn ro*>*}pT,<.*kj. von 7Tt"st nav« mi<-a.. anrJ thev could get none of it ' during the. war."