66 



NA TURE 



>IaV 2 1, 1896 



experiments, and finds it much smaller than Ilerapath did, 

 namely, I '557. 



Prof. Mayer also gave formula; of transmission of Kcintgen rays 

 through glass, tourmaline and herapathite. To determine whether 

 rays just go through or nearly go through, he uses a wire grating 

 which will appear in the picture if rays go through. Trans- 

 mission depends on the thickness of the glass plus the time of 

 exposure. Glass of various thickness is used, one plate being 

 superposed upon another in successive gradations. The eye 

 cannot distinguish a difference less than about l/loo, and this is 

 what i)asses through glass of five millimetres thickness. If we 

 begin with glass l/io millimetre thick, it absorbs l/io of the 

 rays, and each superposed i/io millimetre absorbs l/io of the 

 residue, so that the formula in general is I' = I<!(. It is evident, 

 therefore, that there is no constant ratio of comparison of ab- 

 .sorption by different materials, because the successive ]?owers of 

 "fl" have not the same ratio to each other that the first powers 

 have. In the case of herapathite the absorption {a) is found to 

 be -9382, so the formula becomes V = \ -9382'. The formula for 

 tourmaline is the same as for glass, so tourmaline is a very 

 imperfect substance to use. 



Prof. Ogden N. Rood read a paper detailing his experiments 

 in reflecting the X-rays, which have enabled him to leflect l/26oth 

 part of the rays incident on platinum at an angle of 45° (see 

 Nature, April 30, p. 614). 



Prof. Arthur W. Wright read a paper on the relative perme- 

 ability of magnesium and aluminium by Rontgen rays. He 

 reported experiments showing that magnesium is much more 

 permeable than aluminium. Magnesium is also more readily 

 wrought than aluminium, thus making it much more desirable 

 to use in the investigation of these rays. 



Prof. T. J. J. .See, of Chicago University, read a paper on 

 double star's, giving results of three years' observations. He 

 concludes that at the end of 115 years we know accurately only 

 forty ; that there is only evidence of disturbing bodies in a 

 few cases, which are indecisive ; that great eccentricity of orbit 

 prevails, the average being twelve times as much as that of 

 planetary orbits, and that the law of gravity is rendered prob- 

 able and may be hereafter confirmed by spectroscopic in- 

 vestigation. 



Among other papers read are :— The geological efficacy of 

 alkali carbonate solutions, by E. W. Hilgard, read by G. Brown 

 Goode ; on the colour relations of atoms, ions, and molecules, 

 by M. Carey Lea, read by Ira Renisen ; on the characters 

 of the Otoccelida;, by E. D. Cope ; on the determination of the 

 coefficient of expansion of Jessop's steel, between the limits of 

 o" C. and 64° C. , by the interferential method, by E. \V. Morley 

 and Wm. A. Rogers ; on a remarkable new family of deep-sea 

 Cephalopods {Opistotenthis), and its bearing on moUuscan mor- 

 phology, and on the question of the moUuscan archetype, by 

 A. E. Verrill ; on nthecanthropus erectus from the Tertiary 

 of Java, which was discovered by Dubois in 1S95, by Prof. 

 Marsh ; on the separate measurement, by the interferential 

 method, of the heating effect of pure radiations and of an 

 envelope of heated air, by Wm. A. Rogers ; judgment in sensa- 

 tion and perception, by J. W. Powell ; exhibition of a linkage 

 whose motion shows the laws of refraction of light, by A. M. 

 Mayer ; location in Paris of the [dwelling of Malus, in which 

 he made the discovery of the polarisation of light by reflection, 

 by A. M. Mayer. Ira Remsen read a paper on some studies in 

 chemical equilibrium, and several papers were read by title. 



The Academy adjourned to meet at New York, November 17, 

 t8q6. Wm. H. Hale. 



THE MANUFACTURE OF ARTIFICIAL SILK. 



LANCASHIRE is on the eve of some important expan- 

 sions of the te.xtile trades, for, from an interesting 

 article in the Times, it appears that the manufacture of arti- 

 ficial silk from wood pulp will shortly be added to her industries. 

 At present the wood-silk comes from France, large works 

 having been established at Besan(,-on under patents granted to 

 Count Hilaire de Chardonnet, who discovered the process, 

 and first established in 1S93 the fact that it might be made into a 

 commercial success. The demand for the new commodity in- 

 crea.sed so considerably that the idea of introducing its manufac- 

 ture into ICngland was mooted, with the result that a number of 

 silk and cotton manufacturers met to discuss the question, and 

 finally sent out to Besan9on a deputation, consisting of some of 



NO. 1386, VOL. 54] 



their own number, an engineer, a chemist, and a lawyer, to in- 

 vestigate the subject thoroughly. This was done, and the out- 

 look was found to be so promising that certain concessions have 

 been secured and a company is now in process of formation, and, 

 to begin with, a factory, which will cost ^'30,000, is to Ije built 

 near to Manchester for the manufacture of artificial silk yarn from 

 wood jHilp, for sale to weavers, who will work it up by means ot 

 their existing machinery. The way in which wood pulp can be 

 converted into silk yarn is explained in the Times. The pulp, 

 thoroughly cleansed, and looking very much like thick gum, is 

 put in cylinders, from which it is forced by pneumatic pressure 

 into pipes passing into the spinning department. Here the 

 machinery looks like that employed in Lancashire spinning sheds, 

 except that one of the pipes referred to nms along each set of 

 machines. These pipes are supplied with small taps, fixed close 

 together, and each tap has a glass tube, about the size of a gas- 

 burner, at the extreme point of which is a minute aperture 

 through which the filaments pass. These glass tubes arc known 

 as " glass silkworms," and some 12,000 of them are in use in the 

 factory at Besan9on. The effect of the ]>neumatic pressure in 

 the cylinders referred to above is to force the liquid matter not • 

 only along the iron tubes, but also, when the small taps are 

 turned on, through each of the glass silkworms. It appears 

 there is a scarcely perceptible globule. This a girl touches with 

 her thumb, to which it adheres, and she draws out an almost 

 invisible filament, which she passes through the guides and on to 

 the bobbin. Then, one by one, she takes eight, ten, or twelve 

 other such filaments, according to the thickness of the thread to 

 be made, and passes them through the same guides and on to 

 the same bobbin. This done, she presses them together with her 

 thumb and forefinger, at a certain point between the glass silk- 

 worms and the guides. Not only do they adhere, but thence- 

 forward the filaments will continue to meet and adhere at that 

 point, however long the machinery may be kept running. In 

 this way the whole frame will soon be set at work, the threads 

 not breaking until the bobbin is full, when they break- automat- 

 ically, while they are all of a uniform thickness. The new pro- 

 duct is said to take dye much more readily than the natural silk. 

 The chief difference in appearance between the natural and the 

 artificial silk is in the greater lustre of the latter. The success 

 already secured by the new process in France is such that the 

 introduction of the industry into Lancashire is expected to pro- 

 duce something like revolution in the conditions of trade there, 

 not only by bringing into existence a new occupation, but also 

 by finding more work for a good deal of the weaving machinery 

 that is now only partially employed. 



A THEORY OF THE X-RAYS.^ 

 T^HE principal facts, which any satisfactory theory of the 

 ■*- X-rays is called upon to explain, may be summarised as 

 follows : 



(i) The production of the rays by electric impulse, at the 

 kathode,^ in a highly exhausted enclosure. 



(2) Propagatiim in straight lines and absence of interference, 

 reflection, refraction and polafisalion. 



(3) The importance of density of the medium as the deter- 

 mining factor in the transmission of the rays. 



(4) The production of fluorescence and actinic eft'ect-;, and 

 the action on electrified conductors. 



Two theories have been projjosed to account for these re- 

 markable phenomena: (i) the theory of longitudinal waves; 

 (2) the theory of projected particles. 



In reference to the first theory it may be said that unless it 

 is proved that an oscillatory discharge is essential to the pro- 

 duction of the X-rays, there can be no reason for supposing 

 that these rays are of a periodic nature— that they are wave- 

 motion as commonly understood. The aljsence of interference, 

 reflection and refraction is also a very formidable difticulty. 

 Attempts have been made to account for the absence of these 

 invariable accompaniments of every known form of wave- 

 motion, but, as I think, with very indifferent success. 



The most serious difticulty in the second theory is the 

 attempt to explain the passage of the electrified particles of 

 the residual gas (or of the electrode) through the walls of the 



.^ YTomt'ae.tmericaHjoiimalci/Science, .\fr\\. . . 



- Even should further experiment prove th.-il the X-rays proper originat 

 at the first obstruction encountered by the disch.irge, the fact remains tha 

 this discharge originates at the kathode. 



