270 



NA TURE 



[July 17, 1 1 



altered in twenty-five months one fraction of an ohm, and 

 that it moved briskly up to its maximum, standing there 

 quite long enough for a good observation. Indeed, in 

 spite of its condemnation by a jury of experts over two 

 years ago, it was still so lively that I thought it better to 

 check extra swing by a small platinum paddle 1 cm. 

 square moving in sulphuric acid. 



On a metre scale, at one metre distance, the reflected 

 image in a telescope gave '365 mm. deflection ' with the 

 whole induction current from Prof. Kohlrausch's metre- 

 bridge, as described in my last note. 



The object now was obviously to obtain an independent 

 measure of the actual E.M.F. to which this deflection 

 was due. The quadrant electrometer, or some other 

 delicate potential measurer, of course suggested itself. A 

 trapdoor portable, kindly lent me by Prof. McLeod, re- 

 fused to take notice of my wretched little currents, limited 

 as they are by human susceptibility. I do not possess a 

 quadrant, nor will the Royal Society, though twice asked, 

 lend rue one. Here again my friends at Cooper's Hill 

 came to my rescue, and I have to express my thanks, not 

 only to Prof. McLeod, but also to Prof. Stocker and his 

 excellent demonstrator Mr. Gregory, for their assistance. 

 With my Kohlrausch induction bridge in a big bag I 

 journeyed to Egham, and thence on foot to Cooper's Hill. 



The formula to be made use of was obvious. It is 

 given in Prof. Adams's Cantor lectures, and has been 

 kindly verified for me by P'rof. Hopkinson. In it the 

 needle is connected with one pair of quadrants, so that 

 V 3 = V x . In this case — 



Deflexion = -{V, - K,) 2 . 



Prof. Adams has since shown me a different, and per- 

 haps better, way of working, which I intend to make use 

 of in the future. It was found that the two fine quadrant 

 electrometers at Cooper's Hill College were unavailable ; 

 the one given by Lord Salisbury not admitting of the 

 needle being placed in connection with either pair of 

 quadrants, the other being disabled by some casual 

 contact. We therefore with heavy hearts made a last 

 struggle with the old Elliott pattern and single quadrants. 

 This succeeded admirably, and on a mean of the four best 

 out of six observations, we obtained a deflection of 107 

 with the intermittent current. " In order to be quite sure," 

 Mr. Gregory wrote to me next day, "of the true value of 

 the mean deflection we obtained, I have executtd mea- 

 surements with different numbers of cells. In tl ese, the 

 negative pole was to earth, the positive being connected 

 at will to either pair of quadrants, and the needle also at 

 will to either pair, giving four readings for each observa- 

 tion. I give only means, which agree well. 



E M.F. Dull. k 



21 VoltS ... 3275 



29 ,. •■■ 6375 



47 „ - 16175 



•149 

 •151 

 •146 



Mean ... 

 /• was calculated from the formula 

 * k 



V 



Vtf. 



By calculation, using the mean value of k, the E.M.F. 

 to give a deflection of 107 came out 38. By observation, 

 using an E.M.F. of 38 volts, the deflection was 107-25. 

 This agrees so well with the calculated value that it will 

 be easy to evaluate the E.M.F. corresponding to any de- 

 flection by the above formula." 



The effect of rapid alternations seems to be to lessen 

 the deflection, though Mr. Glazebrook stated, in a paper 

 read before the Physical Society, that with between 10 and 

 120 contacts per second the result, in charging a con- 

 denser, was not perceptible. 



' The bridge arrangement being entirely .Ii 



On the whole therefore, though I agree with Mr. 

 Gregory that we have not obtained a measure of the 

 maximum E.M.F., but only an integration, disregarding 

 sign, the approximation is, I hope, superior to any made 

 before, and affords a good general basis for farther work. 



W. H. Stone 



GAS-BURNERS 1 

 '"THE economist who wished to point the moral of a 



■^ healthy competition in industrial commerce could 

 scarcely find a better instance to his hand than the pro- 

 gress made by gas illumination under the impetus given 

 in the last few years by the rise of electric lighting. It is 

 not overstating the case to say that greater improvement 

 in the use of gas has been made since Jablochkoff intro- 

 duced his electric candle than in the previous sixty years' 

 history of gas lighting. Compared with the recent deve- 

 lopment of invention, the long period of non-competition 

 appears almost stagnant. With the introduction of elec- 

 tricity arose a popular demand for " more light." With a 

 new illuminant competing for favour, consumers growled 

 more openly at "bad gas" and high gas bills. Each 

 advance of the electric light was greeted with acclama- 

 tions by the popular voice, shareholders began to tremble, 

 and gas shares came down with a rush. It was time for 

 gas managers and manufacturers to bestir themselves. 

 The happy days of a monopoly in light seemed over. The 

 consumers have reaped the benefit. Under the stimulus 

 of competition the price of gas has been lowered, im- 

 purities have been cut down. Some half a dozen years 

 ago the great London Companies were endeavouring to 

 prove before a Parliamentary Committee that coal-gas 

 could not be purified from bisulphide of carbon without 

 creating such a nuisance as to be intolerable. Their 

 object was to do away with the lime purifiers, made neces- 

 sary by the regulations of the Gas Referees, and to use 

 only oxide of iron. Since the advent of the electric light 

 not a word has been heard about the impossibility of 

 purifying coal-gas by lime. On the contrary, every effort 

 is now made to supply gas as free from sulphur as 

 possible. But while the gas has thus been improved in 

 quality and lowered in price, a still greater improvement 

 has been effected in the methods of burning it. By the 

 application of the regenerative principle to gas-burners, 

 the illuminative value of coal-gas has been doubled. 



Put in spite of the great advances made in gas-burners, 

 the public have by no means yet reaped the full benefit. 

 Owing to the carelessness of gas-fitters and the ignorance 

 of consumers, the great majority of those who light their 

 houses by gas waste at least 20 per cent, of their gas as 

 an illuminating agent. If the flame smokes, or flickers, 

 or gives a poor light, most people put it down to " bad 

 gas," when in reality the burner is unsuitable, or worn out, 

 or the supply pipes (nearly always too small) are choked. 

 To all who burn coal-gas in their houses, and are troubled 

 with " bad gas," we can heartily recommend " Gas- 

 Burners, Old and New," by Owen Merriman. 



This little book, published at a price which places it 

 within the reach of a large public, describes very plainly 

 in popular language the evolution of the best modern 

 burners of Sugg, of Bray, and of Siemens, from the 

 original "cock-spur burner" of Murdock, and Accum's 

 " tube with a simple orifice, at which the gas issues in a 

 stream, and if once lighted will continue to burn with the 

 most steady and regular light imaginable, as long as the 

 gas is supplied." The illustrations are all that can be 

 desired. 



Owen Merriman has taken pains to insist on the two 

 great desiderata of gas-burners — high temperature and low 

 temperature, but we think he has gone too far in at- 

 tempting to give a popular "theory of luminous combus- 



I Wall 



'Gas-Burners, Old and New." By 0« 

 er King, tS8 4 .) 



(Londo 



