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SC/ENCE-GOSSIJ'. 



3«5 



lO.MiUlTKIi IIV JAMKS (JI'IcK. 



Akiii iciAl. Fl.ic.iir. — Twd of the recent Friday 

 evening discourses at the Royal Institution have 

 lieen of special interest to physicists. The first, 

 which was the opening one of the |)resent series, was 

 given on January' 19 hy Lord Kayleigh on " Flight." 

 After describing the many aeroplanes devised to 

 illustrate the action of Hying, amongst which the 

 Malay kite is one of the simplest, as it does not 

 possess a tail, Lord Kayleigh went on to observe 

 that the best form is that known as the Ilargrave 

 kite. This is a pecidiarly shaped instrument, more 

 like a rectangular skeleton Uix, partly covered with 

 calico, than an ordinary kite. It is, however, very 

 stable in the air, as it depends on side vanes, which, 

 when the kite gets a little out of the wind, tend to 

 bring it back again. The kite was introduced some 

 years ago by Mr. .Xrchibald for meteorological work, 

 and more recently by .Major liaden-Powell, now of 

 South African fame, who has done excellent work in 

 connection with the use of the kite for military pur- 

 poses. Me h.as succeeded in raising a nian from the 

 ground by means of a kite, and has shown that kites 

 could be made useful for reconnoitring purposes. 

 The essential question in connection with the kite is 

 the action of the wind on the aeroplane, but it is 

 different with the flying-machine, which, unlike the 

 kite, is free and unattached to the ground. In 

 regard to the flight of birds, a diflerence is observable 

 between that of small and large ones. A pigeon, 

 for instance, works exceedingly hard, by means of 

 vigorous flapping of wings, to raise itself to the top of 

 a building : whereas the big soaring or sailing flight 

 birds are able to maintain themselves in the air for a 

 considerable time with little or no flapping of the 

 wings or muscular efl'ort. The question of how this 

 soaring is maintained is still a debated one. Natu- 

 ralists are unable to appreciate the mechanical 

 difficulty ; and mechanics say that a bird cannot 

 maintain itself in the air when the latter is moving 

 in a perfectly uniform, horizontal manner. There 

 must be a vertical component. Hirds take ad- 

 vant.age of the relative motion of the diflerent parts 

 of the air they encounter. Those like the albatross 

 take the benefit of the gustiness of the wind. Not 

 only is there pressure underneath the wing of the 

 bird, but suction on its upper surface. If a man 

 raises himself in the air and he is not to fall there 

 must be a downward current of air caused by a 

 screw, and the question is what must lie the size of 

 the screw and the work to be done in order that a 

 human being may be supported. Careful considera- 

 tions show that it is impossible for him, by his own 

 muscular power, to support himself by means of a 

 screw. A bird has an advantage in point of size, 

 and the wings a man would require, if he is to fly 

 with them, would be absurdly large. In the same 

 way the size of a screw would have to be out of pro- 

 portion to anything that could be managed. Mr. 

 Miram Maxim has said that it is only a question of 

 money. 



Sl'ACE TELK<:KAfliy.— The second physical lec- 

 ture referred to was given at the Royal Institution 

 on February 2nd by Signor Marconi before a crowded 

 audience, the subject, as may lie expected, being 

 " Wireless Telegraphy." He sketched in outline the 

 (general work that he and his assistants have lieen 

 doing for the last two years or more. Alluding to 

 the installation of his system Ijctween the .South 

 I'oreland and the Goodwin Sands Lightship, he said 

 the experiments had shown that wireless telegraphy 

 was reliable and certain in operation, lie hoped 

 that before long the Trinity House authorities would 

 be enablctl to establish communication all round the 

 coast with lightships and lighthouses, by means of 

 which a vast amount of properly and many lives might 

 be saved. Signor Marconi then mentioned how, when 

 last returning from America, he opened up wireless 

 communications between the ss. " St. Paul " and one 

 of his signallipg stations on the south coast, when the 

 vessel was sixty miles from land and steaming at 

 twenty knots an hour. At the tardy request of the 

 War Oflice some of his assistants with instruments 

 were sent to .South Africa, and arrived at De Aar camp 

 on December nth. Finding no arrangements made 

 for a supply of the necessary poles, &:c., they manu- 

 factured, with the hearty assistance of Major Baden- 

 I'owell and Captain Kennedy, some kites with which 

 they got over the difficulty. The results at first 

 were not very satisfactory, but eventually com- 

 munication was established between De Aar and 

 the Orange Kiver, a distance of over seventy miles. 

 Stations were then established at Modder River, 

 Belmont, Orange Kiver, and De Aar. They had 

 worked well, and would be invaluable in case the field 

 lines should be cut by the enemy. Signor Marconi 

 said he found it hard to believe the Boers posses.sed 

 any wireless telegraphy instruments. Some intended 

 for them were seized at Cape Town, but thej' were 

 found to be of foreign manufacture. lie remarked 

 he need hardly add that no apparatus had been 

 supplied by him to anyone from whom the Boers 

 could jiossibly obtain them. The lecture was illus- 

 trated by diagrams and a number of lantern slides. 

 Without wishing in any way to lessen the credit due 

 to Marconi for his work in this most important sub- 

 ject, his lecture cannot be considered in (|uite good 

 taste. Had the title been "Marconi Telegraphy," 

 the rcstime would have been a perfect one. Not a 

 single word was said, however, alx)ut other workers 

 and other methods; yet these workers include some 

 of the leading physicists and engineers in the world, 

 and their methods, though ditVering perhaps from 

 that of .Marconi, aim at the same result. Surely one 

 would think that at a Koyal Institution gathering the 

 .solid work of such men as Preece and Lodge should 

 at least have been mentioned. 



A Pilot Torpedo. — The method of protecting 

 special trains from collision by means of a pilot engine 

 has been further practised by the introduction of a 

 specially designed electrical pilot torpedo to protect 

 ships at sea from collision. Its shape resembles that 

 of a Whitehead torpedo, and it is connected to the 

 ship it is to protect by nieans of two pairs of wires. 

 One pair convey the current to the torpedo for driving 

 the motors connected with the screw propcUor ; the 

 other pair are in circuit with an alarm-bell on the 

 ship, and with two special " feelers" at the head of 

 the torpedo, this circuit lx;ing closed when the 

 " feelers " collide with anything. Immediately this 

 happens, a special arrangement reverses the direction 

 of rotation of the motors, making the torpedo recoil. 

 It is not clear how the torpedo is steered. 



