October 20, 1910] 



NATURE 



51, 



motors mounted on a sieel frame furnished with springs 

 to deaden the vibration. Each propeller is driven by its 

 own motor, but, in case of need, one single motor can 

 drive the two propellers at; the same time. The gear for 

 the reduction of speed is placed in the prolongation of the 

 driving shaft, beyond the propeller. The two propellers, 

 of ixjlished wood, have a diameter of 19 feet 8 inches, and 

 are placed laterally in front, one on each side of the car, 

 projecting beyond the sides of the steel frame- 

 work, 'i hey occupy a position midway between the car 

 and the balloon. 1 he tractive power of each propeller is 

 ascertainable at any moment. The dirigible is built to 

 be able to ascend 10 an altitude of 6560 feet, and it is 

 capable of travelling about 750 miles without replenishing 

 its supplies of gas and fuel. 



The Clement-Bayard .\o. 2 left Lamotte-Breuil with a 

 crevi' of seven people, including M. Clement, the designer 

 of the vessel, on October 16 at 7.5 a.m. (G.M.T.), passed 

 over Amiens at 8.29 and Boulogne at 10.15. The Channel 

 was crossed in some fifty-five minutes, and Ashford seen at 

 11.45 a-ni. Tonbridge was passed at 12.29 p.m., the 

 Tower Bridge at 1.4. and Wormwood Scrubbs was reached 

 at 1.25. The whole distance, of nearly 260 miles, was 

 thus covered in a little more than six hours at an average 

 speed of about 43 miles an hour. The greatest altitude 

 attained during the flight was between 800 /eet and 900 

 feet, but most of the travelling was done between 600 feet 

 and 700 feet. The average temperature was 60° F. The 

 success of the enterprise must be attributed largely to the 

 very favourable vi'eather conditions which prevailed during 

 the flight. There was only a slight wind, and it was in 

 a direction which assisted the movement of the airship, 

 so that the demand made upon the power of independent 

 navigability was not great. We still await the construc- 

 tion of an airship which will satisfy the War Office tests, 

 one of which is that the vessel has to traverse a triangular 

 course of 300 miles within a fixed time-limit. When this 

 has been done it will be possible to form a satisfactory 

 estimate of the advantagfs of power-driven airships over 

 the ordinary spherical balloon. 



The America, in which Mr. Wellman w'ith five com- 

 panions made the daring attempt to cross the .Atlantic, 

 is a dirigible of the frameless type ; it is 22S feet long, 

 its greatest diameter 52 feet; and it has a volume of 

 345,000 cubic feet. .According to the Daily Telegraph 

 (under the auspices of which, with the New York Times 

 and other American papers the flight was undertaken), 

 the balloon is composed of three thicknesses of cotton 

 arid silk gummed together with rubber to make it gas- 

 tight, and weighs 4850 lb. Underneath the balloon is 

 suspended by steel cables the car, weighing 4400 lb. This 

 car is built of the highest grade steel tubing, and in places 

 withstands stresses of twelve tons. It is 156 feet in length, 

 and the steel tank at its base is 75 feet long, with a 

 capacity of 1250 gallons of gasoline. The engines, three 

 in number (two of 80 horse-power and a service motor 

 of ten horse-power), are placed in the steel car. Each 

 of the large motors drives a pair of twin screws, and 

 each propulsion system is independent of the other. The 

 motors and other machinery weigh about 1500 lb. An 

 electric light system, a wireless telegraph equipment, and 

 a telephone connecting the different parts of the ship were 

 installed. 



Hanging from the airship by a steel cable is the equili- 

 brator, a part of which floated upon the sea, the other 

 being suspended vertically in the air. The purpose of 

 this is to act as an automatic regulator of the upward and 

 downward movements of the airship. When the ship 

 rises it must lift some of the equilibrator from the sea 

 in order to go up, and this added weight checks the rising 

 movement. Conversely, when change of temperature or 

 accumulation of moisture caused the airship to descend, 

 a greater part of the equilibrator was let down upon the 

 sea, thus reducing the weight carried by the balloon and 

 checking the descent. 



The total supply of gasoline carried was 10,000 lb., or 

 about 1800 gallons, which was considered sufficient to drive 

 the airship from .Atlantic' City to Europe. The distanc* 

 is about 3000 miles. With one engine running the air- 

 ship could make a speed of 20 miles per hour, .and the 

 quantity of gasoline carried would run one engine 200 



NO. 2138, VOL. 84] 



hours. With both engines running the ship's speed ia 

 I still air could be about 2b miles per hour. 



After leaving Atlantic City at 8.5 a.m. on Saturday 

 morning, October 15, the America travelled 20 miles in 

 the first hour, but later the rate was reduced to 15 miles 

 an hour. Nantucket Island, which is about 300 miles 

 from the starting place, was reached in twenty-four hours. 

 A wireless message was received from Mr. ^^'ellman at 

 12.45 p.m. on Sunday, October 10, when the airship 

 passed out of range of communication with Nantucket 

 Island. The vessel was then directed to the north-east, 

 and early on the morning of October 17 was believed to 

 be travelling between Nantucket Island and Nova Scotia. 

 At 4.30 on October iS the airship was sighted in distress 

 by the Royal Mail Steam Packet Company's steamer 

 Trent, and after some difficulty .Mr. Wellman and his 

 crew were rescued and taken on board, the airship being 

 abandoned. The position in which this occurred was lati- 

 tude 35° 43' N. and longitude 68° 18' W., which is nearly 

 400 miles east of Cape Hatteras, on the North Carolina 

 coast. The total distance covered by the airship appears 

 to have been about goo miles, and the duration of the 

 voyage, during which she was in the air continuously, 

 was sixty-nine hours. 



MATHEMATICS AND PHYSICS AT THE 

 BRITISH ASSOCIATION. 

 T^HE address of the president of Section A, Prof. E. W. 

 ■*■ Hobson, was read on Thursday, September i ; this 

 has appeared in full in these columns (N.iture, Sep- 

 tember 1, p. 284). It was succeeded by a paper — probably 

 the most important paper read at the meeting — by Sir 

 J. J. Thomson on positive rays. By the use of very large 

 vacuum tubes Sir Joseph has been able to investigate the 

 discharge at higher vacua than hitherto. Specially study- 

 ing the rays wnich pass through a hole in the kathode^ 

 he detects : — (i) Rays undeviated by magnetic or electric 

 forces. (2j Secondary positive rays, produced by these, 

 which are deflectable by both forces, have a constant 

 velocity of about 2x10° cm. /sec. at all pressures and 

 potential differences. The value of e/m for these is lo*. 

 They are accompanied by negatively charged ones similar 

 in every respect to the positive ones, except in respect to. 

 charge. (3) Rays characteristic of the gases in the tube, 

 conspicuous only when the pressure is low. Their velocity 

 varies with the potential difference. When several gases 

 are present, the maximum kinetic energy of the rays from 

 each gas appears to be the same and equal to that due 

 to a fall through the potential difference between the 

 negative glow and the kathode. The value of e/m is 

 inversely proportional to the atomic weight of the gas. 

 They are probably atoms carrying unit positive charge ; 

 in the case of hvdrogen there are rays corresponding to 

 the molecule as ' well. Some of these have negatively 

 charged rays associated with them. In a magnetic field 

 the rays from a mixture of gases spread out into a sort 

 of spectrum. With carbon monoxide two bands are 

 formed, one due to carbon, the other to oxygen. As 

 exceedingly small quantities of gas may be dealt with in. 

 this way, "it appears probable that interesting results may 

 follow from the application of this method to the analysis 

 of gases in vacuum tubes. (4) Retrograde rays, travelling 

 from the kathode in the same direction as the kathode 

 rays. These are of types (1) and (2). They have negative- 

 constituents. 



Dr. R. A. Houston followed with an exhibition of a. 

 spectrophotometer of the Hiifner type, which he has 

 previously described in the Phil. .Mag. for February, 1908, 

 and witli a description of a new and simple means of 

 producing interference bands. An approximately right- 

 angled prism is placed in front of a slit ; the two emergent 

 beams produce interference bands in front of the prism. 

 This is -tieing used as a student's exercise ; it does not 

 appear, however, that the bands can be put to any prac- 

 tical use. .\ new gvroscopic apparatus was next exhibited 

 by Prof. .A. E. H. Love. The machine consists essentially 

 of a pair of bicycle wheels fixed to a round steel bar as 

 an axle. The bar is prolonged beyond one wheel to carry 

 a wooden wheel, bv means of which it can be set 



