44 



NATURE 



[May 12, 1892 



A very interesting discussion followed the reading of the 

 report, but a great part of this it would be useless to give, as 

 many details of the trial have necessarily been omitted from 

 our brief abstract. 



A paper was next read " On Condensation in Steam-Engine 

 Cylinders during admission." This was a contribution by 

 Lieutenant- Colonel English, of Jarrow. In former papers on 

 this subject the author had given experimental data, but it was 

 objected that he had left out of account the range of temperature 

 in the cylinder. In order to show that this was not the case, 

 he submitted the following formulae, which, he claimed, proved 

 his case. The former papers, a study of which is necessary to 

 a proper understanding of the facts, may be found in the 

 Transactions of the Institution for the years 1887 and 1889. 



In jacketed cylinders the weight of steam condensed per 

 stroke and not re-evaporated at cut-oflf is represented by the 

 expression 



56 ^ (S. - S; 



revs, per second 



Pi. 



where S^ is the unjacketed clearance surface in square feet, Sj 

 the fresh surface exposed during admission up to cut-off, p, the 

 initial density of the steam in pounds per cubic foot, and L 

 the latent hedt of evaporation in thermal units. ' If </ be the 

 diameter of the cylinder in feet, / the length of stroke in feet, 



w the proportion of stroke up to cut-ofF, ju =- ~ , 



2 X area of cylinder 

 and N the number of revolutions per minute ; then S,- = un- 



yUW- 



jacketed clearance surface = — 



- 775 



Weight condensed = 56 x 775 ( t^-ncV- 



Sj = irdml; vrevs. per second 

 and the foregoing expression may be written 



>■ 



v'nV 



8_/ 



2\ ird'^ml 



■/■iml 



Pj is the weight of steam per stroke uucondensed at 

 '»• 

 cutoff, and 868 may be taken as an approximate value for L ; 

 therefore for jacketed cylinders ; 



__ weight condensed _ i f jx _ 2\ 

 weigtit uncondensed /^ \ml lij 



For unjacketed cylindei's a .similar approximate expression is 



^/N \,nl dj 



The author supported his views by means of a voluminous 

 table, in which he gathered together the observed data on a 

 numbtr of steam-engine trials made by various well-known 

 authorities, to which he attached the results obtained by calcu- 

 lation on his system. 



A short discussion fallowed the readmg of this paper, and the 

 meeting was then brought to a conclusion by the usual votes of 

 thanks. 



The summer meeting of the Institution will be held at Ports- 

 mouth, on July 26 to 29. 



THE ROYAL SOCIETY SOIREE. 

 'T'HE annual soiree of the Rojal Society, which took place on 

 Wednesday, May 4, may be said to have been the most 

 successful that has been held for many years. All the necessary 

 arrangements, which were by no means few in number, were 

 carried out without a hitch, while the exhibits were of a most 

 attractive nature. As regards the latter, tfie following are a 

 few notes of the most novel and important objects displayed: — 

 Prof. T. E. Thorpe exhibited a model to illustrate the general 

 phenomena of explosions as brought about by the presence of dust 

 particles, in explanation of the causes of colliery explosions. This 

 apparatus consisted of two long narrow boxes, fitted together in 

 the form of a cross. On the bottom of these boxes was thinly 

 strewn a quantity of fine Lycopodium powder, while at one end 

 of the longer box there was a small chamber in which a blank 

 cartridge was fired. The firing of this cartridge corresponded 

 to the direct action of a " blow-out shot," while the dust raised 



NO. I I 76, VOL. 46] 



by the concussion, which carried the flame throughout the 

 entire apparatus, took the place of the fine coal dust. The 

 apparatus also showed that the progress of such an explosion 

 was always accompanied with increase of violence. 



Prof. Clowes showed an ordinary miner's safety-lamp which 

 had, by a very simple contrivance, been converted into a delicate 

 instrument for detecting minute proportions of fire-damp. To 

 the ordinary burner an additional tube is made to pass through 

 the oil reservoir, one end of it being connected, by means of a 

 flexible tube, with a small portable bottle of compressed 

 hydrogen. The hydrogen when turned on becomes ignited 

 close to the oil burner, the flame of which is extinguished by 

 turning down the wick ; by adjusting the flame of hydrogen to 

 the standard height, a luminous column of light is seen vertically 

 over it, from the behaviour of which the amount of inflammable 

 gas can be directly estimated. At the conclusion of the experi- 

 ment the wick is simply turned up, and ignited from the 

 hydrogen flame ; the latter is then disconnected from the bottle. 

 From 0*25 to 3 per cent, of fire-damp has in this way been 

 estimated, while greater quantities than these have been 

 measured by reducing the size of the flame. 



Vacuum tubes without electrodes, exhibited by Dr. Bottom- 

 ley, These tubes, which were of a variety of shapes and kinds, 

 illustrated very beautifully all the phenomena of stratification. 

 They were sensitive also to magnetic and electro-dynamic in- 

 fluence, and showed the phenomena of molecular bombardment. 

 The brilliant illumination of a piece of Iceland spar contained 

 in a glass sphere afforded an excellent means of displaying the 

 electrical excitements. [For an nccount of experiments with 

 vacuum tubes, see a letter by Mr. Bottomley in Nature, 

 January 6, 1881, vol. xxiii. p. 218.] 



Mr. Cecil Carus- Wilson exhibited some natural and artificial 

 sands, from which he was able to produce many musical notes. 

 These notes, as he explained, were the results of the rubbing 

 together of the surfaces of the grains of sand, but he had met 

 with several sands from which he could not obtain a vestige of 

 a note. One special artificial sand sang only when rubbed in 

 some sort of vessel. 



Apparatus for measuring degrees of incompleteness of colour 

 vision, exhibited by Mr. Brudenell Carter. The object used 

 for the tests is a group of various colours, which were such that 

 they could be seen by either reflected or transmitted light. The 

 amount of illumination that was required to recognize the 

 colours distinctly was a measure of the "degree of incomplete- 

 ness." In order to control this amount of illumination, light 

 of known intensity had to pass through a variable aperture before 

 it fell on the test object, the size of this aperture being read off 

 in square millimetres. 



Captain Weir's azimuth diagram was exhibited by Mr. J. D. 

 Potter. It is claimed for this diagram that betides being most 

 ingenious, it furnishes one of the most successful modes of 

 graphic solution of a mathematical problem that has ever been 

 invented. It is used for finding the true azimuth of a heavenly 

 body, taking into account the ever-changing errors of the 

 compass, which in our days of iron ships have to be so carefully 

 watched and recorded. The errors as usually determined are 

 obtained from observations made of the compass-bearing of a 

 heavenly body (the sun generally being taken) with its true 

 bearing, and it is for the simplification of this method that this 

 azimuth diagram has been found to be practically useful. 

 I Prof. Oliver Lodge had three exhibits. The first was the 

 projection of interference bands on a screen, being produced 

 ! by a modified method of Michelson. Very striking also were 

 i the electric sparks in and to water, illustrating lightning effects 

 and multiple flashes. In a shower, with too great spark-length 

 for a strong discharge, a multitude of violet streams or spurts 

 filled the air, resembling somewhat lightning flashes. The spark 

 to water spread itself out over the surface, showing that the 

 surface layer was a feeble dielectric, while the spark under water 

 was britrf but very vi^dent, treating the water as a dielectric, and 

 producing concussion. The electric retina, illustrating the 

 possible meaning of the rod-and-cone structure, was very in- 

 teresting ; radiation from spheres which were in a suddenly 

 disturbed and oscillatory electrical condition falling upon a 

 graduated series of end-on cylinders, which responded by 

 vibrating transversely. 



Mr. W. Ciookes repeated many of those beautiful ex- 

 periments of electric currents of high potential and extreme 

 frequency that were first carried out by Tesla. The discharges 

 from a battery of Leyden jars were sent through the primary 



