Jtinc 6, 1 889] 



NA TURK 



casual travelling companions, and from writers of the most 

 various degrees of authority, tiiat his statements can lay no claim 

 to the serious attention of students of folk-lore, and present 

 no interest for the English reader. 



SOCIETIES AND ACADEMIES. 



London. 



Physical Society, May 25. — Prof. Reinold, President, in 

 the chair. — The following papers were read: — On a relation 

 existing between the density and refraction of gaseous elements 

 and some of their compounds, by Rev. T. Pelham Dale. In a 

 previous communication the author pointed out a relation 

 between the specific refractive energies of sulphur and selenium, 

 and the present paper deals with similar relations in gaseous 



bodies. On calculating out the values of ^ for the ele- 



d 



mcnts H, O, N, CI, S, P, it was noticed that the logarithms 

 were nearly integral multiples of half the logarithm for H, those 

 for N, CI, and P being double, and S and O three times that 

 number. The value of ju - i for different elements is compared 

 with the jx - I for H, the resulting numbers being, for oxygen 

 2, mercury 7, arsenic 8, and sulphur 12 nearly. Similar calcu- 

 lations are made for the compounds N^O, NO, CO, SO2, Cy, 

 NH3, HCl, HoS, CH4, and Q-sVii, but as the data obtainable 

 are very rough, the numbers are not so closely integral. The 

 author hopes that better data will be furnished by persons having 

 greater facilities than himself for experimental research. Prof. 

 Riicker thought the results obtained pointed towards some rela- 

 tion between the volumes of the molecules of different elements, 

 and at the close of the meeting announced that on working out 

 the relation he found the relative volumes to be a series of 

 numbers in geometrical progression. — On a water-spray influ- 

 ence machine, by Mr. George Fuller. The appiratus is made 

 up of four similar sections, each consisting of a nozzle, a metnl 

 ring, and a metal dish or receiver, arranged about a vertical 

 axis. Pressure-water issues from perforations i/ioo inch in 

 diameter in the nozzles, and passes through the rings into the 

 insulated receivers below. The rings are placed at such a 

 distance below the nozzles as to be about the point where the 

 streams break into spray, and the receivers empty themselves 

 automatically. Calling the consecutive sections i, 2, 3, 4, 

 respectively, the rings of i and 3 are connected to the receiver 

 of 4, and those of 2 and 4 to the receiver of I. The discharge- 

 points are connected with the receivers 2 and 3, and a rapid suc- 

 cession of sparks passes when the water is turned on. Prof. S. 

 P. Thompson inquired whether the length of the spark was 

 limited by leakage along the glass rods or by the spray passing 

 between the receivers, and in reply Mr. Fuller said he thought 

 the former leakage the most important. — Notes on polarized 

 light : {a) on the transition tints of various orders ; {b) lecture 

 illustrations of the rotation of circularly-polarized light ; [c) on 

 the rotation of circularly- polarized and non- polarized light, by 

 Prof S. P. Thompson. The first noie described an inquiry as 

 to what thickness of quartz gives the best "sensitive tint " for. 

 polarimetric work. Blot gave the name to the tint pro- 

 duced by a quartz 34 millimetres thick in a bright field, 

 whereas in most modern poiarimeters the name is given to 

 that produced by 7.7 millimetres of quartz in a daik field. 

 The transition- tints of various orders were exhibited on a 

 diagram of Newton's scale of colours, and by a wedge of 

 selenite. Experiments were made on quartzes of 3I and ii^ 

 mm., giving tints of the first and second order respectively in the 

 bright field, and with a 7^ mm. quartz in a dark field. The 

 3^ was more sensitive than the 11^ to small rotations, but the 

 7.1 mm. seemed the best of the three. Prismatic analysis of the 

 light transmitted by each led to the same conclusion — a new 

 square-ended direct-vision prism built up of a glass prism (angle 

 140') immersed in cinnamic ether being used for thct purpose. 

 The author pointed out that the "sensitive tints" of German 

 opticians are decidedly redder than Biot's, and those generally 

 used in England. In the first apparatus devised under {b), the 

 ray of light is represented by a stretched cord thrown into 

 promiscuous vibration by a tuning-fork, and the polarizer and 

 analyzer are each represented by two plates of glass mounted 

 parallel to each other about a millimetre apart, between which 

 the cord passes. Between the polarizer and analyzer the vibra- 

 tions are in one plane, and they are transmitted or cut off by the 

 analyzer according as its plates are parallel or perpendicular to 

 those of the polarizer. By blowing across one side of the 



spindle-shaped vibrating segment between the crossed plates, the 

 plane of vilralion is slightly rotated, and part is transmitted' 

 through the analyzer. Other experiments illustrating rotation of 

 the plane of polarization weresliown or described, the most con- 

 clusive being a bar of heavy glass placed along with a fish-eye 

 lens between crossed Nicols. On starting a current in a helix 

 surrounding the glass, the black cross formed by the fish- 

 lens is seen to turn round as the current grows. Another 

 piece of apparatus to illustrate Fresnel's view of the circularly 

 polarized waves in quartz consists of two equal coplanar disks 

 rotating in oppo.>ite directions, and carrying pins on which the 

 extremities of a double pantograph arrangement are pivoted. 

 The middle point of the link-work describes a line perpendicular 

 or inclined to the line of centres of the di^ks according as the 

 phases of the pins are the same or different, {c) In speaking 

 of rotary polarization it is customary to say that the plane of 

 polarization is rotated, but the author thinks it is equally correct 

 to say that the light itself is rotated. Prof. Stefan's and Prof. 

 Abbe's experiments bearing on the subject were described, and 

 to demonstrate that ordinary light may be rotated, a biquartz 

 was placed between a Fresnel biprism and the screen on which 

 the interference fringes were formed. By using quartzes of 

 thickness sufficient to rotate each beam 45°, the interference 

 fringes are caused to disappear, and on inserting a bar 

 of heavy glass in each of the pencils, and magnetizing one 

 of them, the fringes reappear. Mr. Glazebrook thought the 

 reason why3f mm. quartzes were more sensitive than \i\ might 

 be seen by considering the sector-shaped spectrum in which the 

 rays are spread out by the quartz, for with the thick piece the 

 angle of the sector will be three times that with the thin one, and 

 hence, in the latter case, a greater change of colour is produced 

 by a given small rotation. Mr. Ward strongly condemned the 

 use of biquartzes for rotation measurements, for he found it im- 

 possible to get them cut with such accuracy as to give a uniform 

 tint ; and if the light be slightly elliptically polarized, consider- 

 able error may be introduced. Speaking of magnetic rotation, 

 he thought Fresnel's explanation unsatisfactory, and considered 

 it probable that the rotary character of the magnetic field in 

 creases the period of one and decreases that of the other circular 

 wave, their velocities remaining the same. As regards quartz, 

 he believes the rotary action due to the light itself (probably an 

 effect of the longitudinal wave), and not to any peculiar crystal- 

 line structure of the quartz, for liquids exhibit similar phe- 

 nomena. Dr. Thompson, in reply, said Mr. Glazebrook's 

 explanation of the difference in sensibility of the quartzes of 

 various thicknesses was not quite satisfactory, for the reasoning 

 would lead one to expect the 3f millimetres to be most sensitive, 

 whereas experiment showed that the 7! millimetres was best. 

 He quite agreed with Mr. Ward about the defects of the bi- 

 quartz, and thought the shadow method preferable in many cases. 

 On the other hand, he was disposed to believe that the rotary 

 power of quartz wa^ a result of its crystalline structure, for fused 

 quartz possessed no such property. As regards liquids. Dr. 

 Thompson thought the rotation due to some kind of skew sym- 

 metry possessed by the molecules, the average effect of w hich is, 

 observed. — On the molecular weight of caoutchouc and other 

 colloid bodies, by Dr. J. H. Gladstone, F. U.S., and Mr. W. 

 Hibbert. '1 his paper gives the results of determinations made 

 by Raoult's method, the reliability of which was first tested by 

 preliminary experiments on substances of known mohcular 

 weights, and found to be fairly satisfactory. The experiments 

 on caoutchouc give a very high value (above 6000), thus con- 

 firming the author's previous impression that it was a colloid. 

 Similar experiments were made on gum-arabic, caramel, albu- 

 men, and ferric and aluminic hydrates, all of which were found 

 to have high molecular weights. All the experiments confirm 

 the belief that the molecule of a colloidal substance is an 

 aggregate of a very great number of atoms. 



Edinburgit. 



Royal Society, May 20. — Sheriff Forbes Irvine, Vice-Presi- 

 dent, in the chair. — A paper, by Prof. Letts and Mr. R. F. Blake, 

 on the identity of Hofmann's "dibenzyl phosphine " with oxide of 

 tribenzyl-phosphine, and on some other points connected with the 

 phosphorized derivatives of benzyl, was read. — Sir W. Turner 

 communicated a paper by Dr. D, Hepburn, on the development 

 of diarihrodial joints in birds and mammals, — Dr. G. Sims 

 Woodhead communicated observations by Mr. D. McAlpine on 

 the progressive movement of detached ciliated portions of frogs- 

 and tortoises, and also observations on the prc^ression, pulsation^ 



