94 



NA rURE 



[May 23, 1889 



Prof. Fitzgerald requested Dr. Thompson to investigate the 

 effects of displacement-currents and of changing vector potential, 

 and pointed out that in a single medium the former can produce 

 no magnetic effect. As regards fields containing different 

 media, he said the calculations would be complicated by the 

 spurious charges on the separating surfaces. Dr. Lodge, in 

 reply, said he had calculated the momentum to be expected in 

 one arrangement of his experiment in which a suspended alu- 

 minium cylinder surrounds one limb of a rectangular magnetic 

 circuit which formed the core of an induction coil ; one end of 

 the secondary was put to the core and the other to the cylinder, 

 thus forming a condenser. The result came out about 10"" dyne 

 second, but he could not say whether such a small quantity was 

 -observable. — On the concentration of electric radiati)n by lenses, 

 by Prof. O. J. Lodge, F.R.S., and Dr. James L. Howard. The 

 authors' first attempts at concentration were made with mirrors 

 ■on a comparatively small scale, and, owing to the difificulties 

 ■experienced, it was considered advisable to try lenses. Two 

 'large cylindrical ones of piano-hyperbolic section were cast of 

 mineral pitch in zinc moulds, the plane faces being nearly a metre 

 square, the thickness at vertex 21 centimetres, and each lens 

 weighed about 3 cwt. The eccentricity of. the hyperbola was made 

 I "7, to approximate to the index of refraction of the substance. 

 The lenses were mounted about 6 feet apart, with their plane 

 faces parallel, and towards each other on a table in the College 

 corridor, and an oscillator was placed about the principal f ical 

 line of one of them at a distance of 51 centimetres from the 

 vertex. The field wa5 expljred by a linear receiver made out of 

 two pieces of copper wire mounted in line on a piece of wood, 

 and the air-gap fietweei their inner ends was adjustable by a 

 screw. When the oscillator worked satisfactorily, the receiver 

 would respond at about 120 centimetres, and with the lenses the 

 distance was 45c. The receiver responded anywhere be- 

 tween the lenses, and within the wedge between the second 

 lens and its focal line, the boundaries being clearly defined, 

 but no special concentration was noticed about the focus. 

 Interference experiments were carried out by placing a sheet of 

 metal against the flat face of the second lens, and determining 

 the positions of minimu n intensity between the lenses. The 

 distance between these points was 50 '5 centimetres, correspond- 

 ing with a wave-length of loi centimetres, whereas the calculated 

 wave-length of the oscillator was 100 centimetres. Prof Fitz- 

 gerald congratulated the authors on their success, and also 

 pointed out that although large oscillators give good results at 

 distances within a few wave-lengths, yet at greater distances 

 small ones were decidedly superior, owing to the energy of 

 radiation varying as the fourth power of th-i rapidity. He had 

 recently made experiments on electric radiations analogous to 

 Newton's rings, and had successfully observed the central dark 

 spot and the first dark band. Referring to Dr. Lodge's experi- 

 ments, he inquired whether any traces of diffraciion were 

 observed near the boundary of the bundle of rays between 

 the lenses. Speaking of polarization experiments, Prof. Fitz- 

 gerald said waves reflected from films of water exhibited no 

 polarization, whereas those reflected from non-conductors were 

 completely polarized. In reply, Dr. Lodge said no diffraction- 

 effects had been observed, but in the interference-experiments to 

 determine wave-length, the positions of minimum effect were 

 very decided. — The President, in proposing that the thanks of 

 the meeting be given to the authors of the papers, congratulated 

 the Society on the presence of both Dr. Lodge and Prof. Fitz- 

 gerald on the present occasion, when subjects with which they 

 were so well acquainted were brought before the meeting. 



Chemical Society, May 2.— Dr. W. J. Russell, F.R.S , 

 President, in the chair. — The following papers were read : — 

 Thiophosphoryl fluoride, by Prof. T. E. Thorpe, F.R.S., and 

 Mr. W. J. Rodger. Thiophosphoryl fluoride, PSF3, may be 

 prepared by the action of arsenic trifluoride on thiophosphoryl 

 chloride, or by heating a mixture of bismuth trifluoride or lead 

 fluoride with phosphorus pentasulphide in a leaden vessel at a 

 temperature not exceeding 250°. It is a transparent colourless 

 gas, which under a pressure of ten to eleven atmospheres at 

 ordinary temperatures condenses to a colourless, mobile liquid. 

 It is slowly decomposed by water into sulphuretted hydrogen, 

 phosphoric acid, and hydrogen fluoride, but does not attack 

 mercury, and can be stored in a glass gas-holder. In air it is 

 spontaneously inflammable, burning with a greyish-green flame 

 forming phosphorus pentafluoride, phosphorus pentoxide, and 

 sulphur dioxide, and it spontaneously explodes with oxygen. 

 When heated, or subjected to electric sparks, it is decomposed 



with separation of sulphur and phosphorus, and formation of 

 phosphorus trifluoride, and eventually phosphorus pentafluoride, 

 whilst if the heating be effected in a glass tube at a sufficiently 

 high temperature the gas is ultimately converted into silicon 

 tetrafluoride. Thiophosphoryl fluoride combines with ammonia 

 forming a solid product P(NH2)2SF, and when shaken with a 

 moderately strong solution of alkali it is absorbed with the for- 

 mation of a thiophosphate and a fluoride. — The boiling-point of 

 sodium and potassium, by Mr. E. P. Perman. Sodium and 

 potassium were boiled in a hollow iron ball which was heated by 

 means of a blowpipe ; the temperature was found in each case by 

 means of an air thermometer consisting of a glass bulb with a 

 capillary stem which was lowered into the vapour, sealed and 

 broken open underwater. The mean result for sodium was 742^, 

 and for potassium 667°, — Note on the heat of neutralization of 

 sulphuric acid, by Mr. S. U. Pickering. Calculating the value 

 of the heat of neutralization of sulphuric acid in infinity of water 

 from the results of a series of experiments on the dilution of the 

 acid, the author finds that it becomes reduced to 28,197 cal., a 

 value within experimental error, the same as that of two mole- 

 cules of hydrogen chloride. — a-codiacetylpentaneand a tw-diben- 

 zoylpentane, by Dr. F. S. Kipping and Prof. W. H. Perkin. 

 — Acetopropyl- and acetobutyl-alcohol, by Dr. H. G. Colman 

 and Prof. W. H. Perkin. 



Royal Meteorological Society, May 15. — Dr. W. Marcet, 

 F.R.S., President, in the chair. — The following papers were 

 read : — Account (if some experiments made to investigate the 

 connection between the pressure and velocity of the wind, by 

 Mr. W. H. Dines. These experiments were made for the pur- 

 pose of determining the relation between the velocity of the 

 wind and the pressure it exerts upon obstacles of various kinds 

 exposed to it. The pressure-plates were placed at the end of 

 the long arm of a whirling machine which was rotated by steam 

 power. The author gives the results of experiments with about 

 twenty-five different kinds of pressure- plates. The pressure 

 upon a plane area of fairly compact form is about i^ pounds per 

 square foot, at a velocity of twenty- one miles per hour; or, in 

 other words, a pressure of i pound per square foot is caused by 

 a wind of a little more than seventeen miles per hour. The 

 pressure upon the same area i^ increased by increasing the peri- 

 meter. The pressure upon a ^-foot plate is proportionally less 

 than that upon a plate either half or double its size. The pressure 

 upon any surface is but slightly altered by a cone or rim project- 

 ing at the back, a cone seeming to cause a slight increase, but a 

 rim having apparently no effect. — On an improved method of 

 preparing ozone paper, and other forms of the test, with starch 

 and potassium iodide, by Dr. C. H. Blackley. Some years ago 

 the author made some experiments with the ordinary ozone test- 

 papers, but found that the papers did not always give the same 

 result when two or more were exposed under precisely the same 

 conditions. He subsequently tried what reaction would take 

 place between unboiled starch and potassium iodide when exposed 

 to the influence of ozone ; but the difficulty of getting this spread 

 evenly upon paper by hand so as to insure a perfectly even tint 

 after being acted upon by ozone led him to devise a new method of 

 accomplishing this. Briefly described, it may be said to be a method 

 by which the starch is deposited on the surface of the paper by pre- 

 cipitation, and for delicacy and precision in regulating the 

 quantity on any given surface leaves very little to be desired. — 

 Notes on the climate of Akassa, Niger Territory, by Mr. F. 

 Russell. This paper gives the results of observations made from 

 February 1887 to October 1888 at Akassa, which is the seaport 

 and principal depot of the Royal Niger Company, and is situated 

 at the mouth of the River Nun in the Niger Delta. — Wind 

 storm at Sydney, New South Wales, on January 27, 1889, by 

 Mr. H. C. Russell, F.R.S. 



Geological Society, May 8.— W. T. Blanford, F.R.S., 

 President, in the chair. — The following communications were 

 read : — The rocks of Alderney and the Casquets, by the Rev. 

 Edwin Hill. The author in this paper described Alderney, 

 Burhou, with its surrounding reefs, and the remoter cluster of 

 the Casquets, all included within an area about ten miles long. 

 Thereadingof thepaperwasfollowed bya discussion, in which the 

 President, Prof. Bonney, Dr. Woodward, Dr. Hicks, and others 

 took part, — On the Ashprington volcanic series of South Devon, 

 by the late Arthur Champernowne. Communicated by Dr. A. 

 Geikie, F. R. S. The author described the general characters of 

 the volcanic rocks that occupy a considerable area of the country 

 around Ashprington, near Totnes. They comprise tuffs and 



