294 



SCIENCE-GOSSIP. 



out a long slender bifid rostrum ; palpi very long 

 and slender, extending beyond the tip of the 

 rostrum and bearing towards the extremities a few 

 fine sitae ; legs of moderate and nearly equal 

 length, terminated by two simple claws ; eyes 

 three, one behind the base of the head, the others 

 near the origin of the second pair of legs. 



I was quite unable to identify it myself. Having 

 found it in fresh water, I did not suspect it to b^e 

 one of the Halacaridae ; so I communicated with 

 Mr. C. D. Soar, and sent some to him for inspection. 

 He has no doubt about it being one of the 

 Halacaridae, and believes it to be Raphignathus 

 fakatus Hodge. How it came to be found in 

 fresh water is a puzzle, as the canal has no direct 

 communications with the sea, from which it is 

 far away. I shall be glad to know if any of 

 your numerous readers have found this or other 

 members of the family so situated, or can throw 

 any light on this apparently strange occurrence. 

 R. Macer, F.R.M.S. 

 23, Wingmore Road, Loughboro' Junction, S.E. 



WATKIN'S MOUNTAIN ANEROID. 



T\ /["OUNTAINEERS and explorers have long felt 

 a want of confidence in aneroid barometers, 

 as even the best have been liable to considerable 

 error in their readings. Mr. Edward Whymper, the 

 celebrated Alpine climber, had drawn attention to 

 this fact so long ago as 1861 ; and now he in- 

 troduces us to a new form of this instrument 

 wherein the error is so fractional that for practical 

 purposes it may be said to be correct, as it deviates 

 no more than xttimhmt °f an inch. The new instru- 

 ment is the invention of Col. H. Watkin, C.B., 

 Chief Inspector of Position Finding in the War 

 Department. This aneroid attains its accuracy 

 in consequence of Col. Watkin designing an 

 arrangement for putting out of gear, or throwing 

 out of action, the barometer when not in use. The 

 result is that, with requisite attention and quick use, 

 Mr. Whymper states that extraordinary results may 

 be obtained with Watkin's Mountain Aneroid in 

 observations made for altitude, and in determining 

 differences of level. Mr. J. J. Hicks, of 8, Hatton 

 Garden, London, makes these new instruments on 

 an especial design for mountain travelling and for 

 survey work in hilly regions. This aneroid, four 

 and a-half inches in diameter, and reading to 0-05 of 

 an inch, the scale being from thirty-one to seventeen 

 inches, with leather case and sling, weighs two 

 and a-half pounds. The usual type of aneroid 

 barometer has often played curious tricks upon 

 mountaineers, and caused them to report altitudes 

 far out of the actual measurements. These errors 

 have extended to as much as 2,000 feet. For 

 scientific research with the aid of balloons, Col. 

 Watkin's instrument will be of immense value. 



EXPLOSIVE VALUE OF 



ACETYLENE. 



TOURING a series of experiments that have 

 recently been made at Leeds to determine 

 the value of the application of acetylene gas 

 to internal combustion engines, some additions 

 have been made to our knowledge of the explosive 

 properties of acetylene. Mr. Frederick Grover, 

 consulting engineer at Leeds, has published, 

 these (!). He found that no weaker mixture than 

 eighteen volumes of air to one of acetylene gas 

 could be exploded at atmospheric pressure, fifteen 

 to one being the weakest mixture of coal-gas and air 

 that can be fired under the same conditions. The 

 researches with regard to the use of acetylene in 

 engines where coal-gas is now ordinarily used 

 show that it will compete effectually with other 

 methods of obtaining motive-power. The efficiency 

 of acetylene motors, Mr. Grover writes, should be 

 higher than that of any other heat motor. He 

 is of opinion that this will reach thirty-five per 

 cent., chiefly by an increase in the speed of revolu- 

 tion. At a thermal efficiency of thirty per cent., 

 the consumption of gas would be 6'i cubic feet per 

 horse-power per hour. 



The convenient and simple method in which 

 acetylene can be generated, makes it a very 

 valuable agent for propelling light vehicles. A 

 carriage with a load of one ton could run for ten 

 hours on sixty pounds of carbide with about half 

 that weight of water. The space required for 

 storing the carbide would be only 2^- cubic feet, if 

 it were broken into small pieces. Room would be 

 required, also, for about three and a-half gallons 

 of water and a small gas-holder. 



The experiments reported by Mr. Grover are 

 undoubtedly of great value, and will clear the way 

 towards the development of an efficient motor. 

 We would, however, like to endorse the warning 

 of the author, that those whose attention is turned 

 in this direction, should remember to make care- 

 ful tests of the working powers of their motors. 

 The researches into the explosive capabilities of 

 acetylene were carried out by Mr. Grover in 

 the following manner: "A known volume of 

 acetylene gas was admitted to a cylinder, and 

 time allowed for its diffusion therein. The mixture 

 was ignited by electricity, and pressure developed 

 was measured by means of a Crosby indicator, the 

 pencil of which worked upon a drum revolving at 

 a known speed. In this way the proportions of 

 acetylene and air, the time taken to complete the 

 inflammation, and the pressures developed were 

 observed." 



no, Strand, London. F. WlNSTONE. 



(') " Experiments on the Pressure and Explosive Efficiency 

 of Mixtures of Acetylene and Air." By Frederick Grover, 

 A.M. Inst. C.E., etc. 22 pp. 8 in. x 6£ in. Illustrated. (Leeds: 

 Jowett & Sovvry, 1898). is. 



