46 



SCIENTIFIC NEWS. 



[April 1st, 1 5 



for the whole of nature, so these 120 elements, by being combined 

 again and again, explained the whole of our language and the whole of 

 our thought. Whatever we think, we think by means of 120 funda- 

 mental concepts, or possibly with even fewer. 



A DISCOURSE at this institution was given last month by Captain 

 W. de W. Abney, R.E., the subject being " Sunlight Colours." 

 The facts brought forward were, the lecturer said, the result of experi- 

 ments conducted conjointly with General Festing, R.E. An important 

 point to be recognised was that different people had very different 

 powers of appreciating colours. What was called roughly colour blind- 

 ness had long been known, but a more delicate test had been tried on a 

 large number of people, including many distinguished artists. The 

 colours of the spectrum were taken in succession, and tested for the 

 recognition of the intensity with which each colour was seen. Few could 

 recognise equally throughout, and those whose perceptive powers were 

 good for the red end failed in a large percentage in the blue, and vice 

 versa. Half of the artists could only see three-fourths of the red. Pro- 

 fessor Tyndall's now well-known theory of the "scattering of light by 

 fine particles " was referred to as producing the distant blues in what 

 artists called atmospheric effects. But there was another effect of fine 

 particles which was illustrated in several ways. One of the most strik- 

 ing of these was with a turbid solution of mastic, gradually becoming 

 more turbid. In alcohol mastic was soluble, in water it was not. A 

 beam of light was first shown passed through a clear alcohol solution 

 of it, and through a prism which split it up into a spectrum bind. The 

 addition of water to the solution caused fine particles to form, increasing 

 in number, and hence increasing the turbidity of the solution. As this 

 proceeded it was seen that the spectrum commenced to vanish at the 

 blue end, gradually disappearing to the red, which was the last portion 

 left. This was exactly what was obtained in some sunsets when the air 

 was misty ; the sunlight from the yellow portion of the spectrum being 

 gradually cut off, till the orange, and then only the red, rays were left. 

 An artificial sunset on this principle was shown most satisfactorily. A 

 number of photographs were also shown, taken at different altitudes in 

 Alpine regions, and exhibiting how " atmospheric effects " lessened as 

 the dryer air was reached. 



THE INSTITUTION OF CIVIL ENGINEERS. 



AT the meeting on Tuesday, the 15th of March, a paper was read 

 on " The Treatment of Gun-Steel," by Col. Eardley Maitland, 

 R.A., the Superintendent of the Royal Gun-Factory, Woolwich. 



It was stated that gun-steel as used in England, and practically by 

 two other gun-making nations (France and Germany), was a ductile 

 material, a test-specimen of which broke under tensile strain at about 

 30 tons per square inch in the soft or annealed state, and at about 45 

 tons per square inch when hardened by being plunged, at a tempera- 

 ture of 1,450° F. , into a bath of cool oil. It contained from o'25 to o'5 

 per cent, of carbon, and from o'8 to O'05 per cent, of manganese. The 

 author proceeded to describe in detail the successive steps by which he 

 had sought to estimate the value of oil-hardening. From a comparison 

 of thousands of results he had formed the opinion that, taking the 

 breaking-strain after oil-hardening as the datum, the limit of elasticity in 

 the unhardened state rose with the proportion of marganese ; and that 

 the effect of hardening in oil increased with the proportion of carbon, 

 raising both the elastic limit and the breaking- strain more than in the 

 case of steel with a higher proportion of manganese. The condition cf 

 strain, however, of pieces tested in the machine differed from that ex- 

 perienced by the metal when built up and used as a gun. For 

 example, when the copper cylinder of a crusher-gauge was repeatedly 

 subjected to the same slowly-applied motion in a machine, no change 

 was produced after the first trials ; but if the cylinder were compressed 

 to the same extent by a falling weight, or blow, subsequent equal blows 

 compressed it still further at each trial. If two gauges were put into 

 the chamber of a gun, and ten rounds fired with a suitable charge, one 

 gauge being left untouched, but the copper cylinder of the other gauge 

 being changed after each round, it would be found that the gauge 

 which withstood ten rounds would simply indicate the highest pressure 

 attained as recorded by the gauge which had been adjusted each time. 

 If, however, an unsuitable charge had been used, and had set up a 

 violent dynamic, or " wave," action, the gauge which had withstood 

 ten rounds would indicate a higher pressure than that of any single round. 

 Hence there was a certain resemblance between the action of suitable 

 powder and the pressure in the machine. It had been noticed that in cases of 

 bursting, the fracture, whether the gun were of cast-iron, or wrought- 

 iron, or of steel, was invariably short and granular. It was formerly as- 

 sumed in explanation of this that the slow pull of the machine did not at 

 all represent the sudden strain put on the material when used as a gun. 

 In order to test the truth of this assumption, a test-specimen was 

 screwed into blocks, one above and one below, so that the whole falling 

 a short distance, the top block was arrested, and the weight of the lower 

 one subjected the specimen to sudden tensile-strain. The result of 

 several experiments was that the elongation, instead of being about 27 

 per cent., as was expected, was about 47 per cent. This unexpected 



result determined the author to try the result of explosives. A strong 

 tube was prepared by being accurately bored and furnished in the 

 middle with a radial vent and a radial crusher-gauge. Plugs of steel, 

 fitting the bore of the tube, were screwed on to each end of a specimen ; 

 these plugs were passed into the tube, the annular space around the 

 specimen being filled in some cases with quick-burning paper, and in 

 others with gun-cotton, air-spaced. On the charges being exploded 

 through the vent, the plugs were driven violently out of the tubes, in 

 opposite directions, each carrying one-half of the specimen. The elon- 

 gations under these tests varied from 47 per cent, to 62 per cent., the 

 fracture in all cases being silky and fibrous. With the largest charges 

 of gun-cotton tried, the specimens in several ca.ses broke in two places, 

 the central piece being cigar-shaped. The results of these, and of other 

 trials with tube-shaped specimens, and with steels of soft, medium, and 

 hard quality, had convinced the author that the remarkable shortness 

 of fracture noticed when a gun burst was a false indication of the quality 

 of the metal. The true indication would be obtained by putting together 

 the pieces and measuring the stretch. 



The subject of erosion of the bore had been engaging the attention 

 of the officers of the Royal Gun-Factory, and a great number of expe- 

 riments had been made to ascertain the qualites of steel best suited to 

 resist it. The details would be found in a joint paper by the author 

 and Sir Frederick Abel, in \h^ Journal of the Iron and Steel Institute, 

 October, 18S6. 



The author then described in detail the long series of experiments, 

 given in the appendix to this paper, made with the view mainly of de- 

 termining the tensile strength of specimens cut from ingots hardened in 

 oil, and unhardened, with and across the grain, and submitted, in the 

 ingot, to varying amounts of work. Judging from the behaviour of 

 specimens, there appeared to be a decided benefit to the steel in oil- 

 hardening and annealing, even though the annealing undid the harden- 

 ing ; and as every nation making great guns used the oil-hardening 

 process, it must be assumed that there were strong reasons for its adop- 

 tion. Nevertheless, with forgings of large size, the oil-hardening was 

 far less active, and very far less uniform than with test-pieces ; and it 

 becaine a serious question whether the double process of hardening 

 and annealing acted so beneficially on the steel as to compensate for 

 the risks incurred in setting up internal strain. 



In conclusion, the paper described the process of building up the 

 complete gun by shrinking. The formulas used at the Royal Gun- 

 Factory for this purpose were, in the author's opinion, thoroughly 

 practical and trustworthy. 



THE GEOLOGICAL SOCIETY OF LONDON. 



ON the i8th of February last, Professor Judd, F.R.S., the Presi- 

 dent, presented the Wollaston Gold Medal to Mr. J. W. Hulke, 

 F.R.S., and the balance of the proceeds of the WooUaston Donation 

 Fund to Mr. B. N. Peach, F.G.S. To the Rev. E. B. Brodie, M.A., 

 F.G.S., he presented the Murchison Medal, and the balance of the pro- 

 ceeds of the Murchison Geological Fund to Mr. R. Kidston, F G.S. 

 (by deputy). The Lyell Medal was awarded to Mr. Samuel AUport, 

 F.G.S. (by deputy), and the balance of the proceeds of the Lyell 

 Geological Fund to the Rev. O. Fisher, M.A., F.G.S. The Bigsby 

 Gold Medal was presented to Professor C. Lapworth, LL.D., F.G S. 

 The President then read his Anniversary Address, in which, after con- 

 gratulating the Society on its present condition and prospects, and re- 

 ferring to some of the more notable incidents in the history of Geologi- 

 cal Science during the past year, he proceede d to discuss the past and 

 present relations between Mineralogy and the Biological Sciences. After 

 insisting that the supposed distinction between living and non-living 

 matter was not a fundamental one, he maintained that minerals resemble 

 animals in possessing definite organisation, and in going through regular 

 cycles of change. He further pointed out that, in the course of its 

 development. Mineralogy was now exactly following in the same line 

 which had been already taken by Zoology and Botany. He expressed 

 his conviction that Geology and Mineralogy were powerful for mutual 

 help, and that the latter science, now passing from the classificatory 

 stage, had a great future before it. 



THE LONDON SANITARY PROTECTION ASSOCIATION. 



THE sixth annual general meeting of this association was held on 

 the 25th ult., at Adam-street, Adelphi, Lord Chelmsford in the 

 chair. The chairman read the report of the council, which stated that 

 during 18S6 312 old members had left the association, but 406 new 

 members had joined, which brought the total membership up to 1,144. 

 The number of houses inspected by the engineers of the association 

 during 18S6 had been 39S, 59 per cent, of which had been found more 

 or less unsanitary. This was rather higher than the average percentage 

 of the five previous years. The total number of houses inspected since 

 the formation of the association was 2,210. In most of these the sani- 

 tary arrangements had been either rendered perfect or very much im- 

 proved. The council had reason to believe that the improved sanitary 

 state of these houses did not represent the whole benefit done by the 

 association. 



