June 29, 191 1] 



NATURE 



607 



this theory to the study of the action of diuretics in 

 animals in which the blood pressure has been lowered so 

 far that propulsion can no longer occur, we obtain evidence 

 as to the parts of the renal tubules acted upon by these 

 different substances. — A. R. Cushny : The action of 

 Senecio alkaloids and the causation of hepatic cirrhosis in 

 cattle. \'arious species of Senecio (ragwort) have been 

 shown to induce fatal poisoning in cattle and horses in 

 South Africa, Canada, and New Zealand. The alkaloids 

 of one of these species were isolated by Watt, and their 

 pharmacological examination shows that they induce the 

 same symptoms as the entire plant. The Senecio species 

 in this country proved non-toxic, except the common 

 groundsel (S. vulgaris), and extracts from the ragwort 

 grown in Canada, where the plant is poisonous, proved 

 devoid of action also. This may, however, be due to the 

 season at which the plant was gathered. — G. Buchanan : 

 Note on developmental forms of T. brucei (pecaudi) in 

 the internal organs, axillary glands, and bone-marrow of 

 the gerbil. — Captain W. B. Fry : A preliminary note on 

 the extrusion of granules by trypanosomes. 



Physical Society, June 9. — Prof. H. L. Callendar, F.R.S., 

 in the chair. — W. Mason : The Liiders' lines on mild 

 steel. Previous investigations have shown that Liiders' 

 lines on specimens of mild steel and wrought iron, strained 

 in tension, are inclined at about 50° to the axis of pull. 

 For tests in compression the information available is not 

 precise, and though the angle of the lines with the direc- 

 tion of the compression is commonly understood to be 

 about 40°, some doubt has been thrown on this point. 

 The author had found previously that the lines are well 

 developed on the surface of mild steel tubes. Since it was 

 easy to obtain a compressive stress of practically uniform 

 distribution in tubes under end pressure, while at the 

 same time a hoop tensile stress could be induced by 

 internal fluid pressure, the author confined his attention to 

 the lines on tubular specimens. These were of mild steel, 

 either hot or cold drawn, and most of them were annealed. 

 The Liiders' lines on the outer surface appeared at the 

 yield point indicated by the extensometer, i.e. their appear- 

 ance coincided with the commencement of the large 

 " yield " strain. In all cases where there were lines on 

 the inner and outer surfaces of a tube, an inner and outer 

 line, and also the ends of these lines, were found to be 

 radially opposite, showing that the lines were traces of 

 surfaces or canals of disturbance which passed through 

 the tube wall, and indicating, moreover, that the disturb- 

 ance spread spirally onwards, and not outwardly from a 

 line initially formed on the more severely stressed inner 

 surface. The conclusion is drawn that the Liiders' 

 surfaces have the same, or approximately the same, in- 

 clination to an axis of simple pull or simple push. With 

 stresses of opposite sign at right angles to each other, the 

 lines and surfaces are more inclined to the stress of 

 greater intensity, and with equal intensities the surfaces 

 are at about 45°. — Prof. S. P. Thompson : A new method 

 of harmonic analysis by averaging selected ordinates. 

 Assume with Fourier that the curve representing any 

 periodic single-valued function of x may be expressed by 

 the harmonic series 



y = Ai sin .-vr-l-Aj sin 2X-I-A, sin 3a;-|- 



-hB, cos AC-I-B, cos 2X-i-B3 cos 3x:. 



Then to find the coefficient of any term, A„ tr B„, it 

 suffices — subject to a limitation stated below — to measure 

 off on the curve an equidistant ordinates over one period, 

 that is, spaced at successive intervals apart of nfn. Then, 

 having reversed the sign of every alternate ordinate, the 

 simple algebraic mean of them gives the coefficient sought. 

 For cosine-coefficients the first ordinate must be taken at 

 the origin, while for sine-coefficients the first _ ordinate 

 must be taken at a point Jir/n from the origin. The 

 process is much facilitated by the use of templates^ of 

 transparent celluloid having equispaced vertical lines 

 engraved upon them. They are laid down on the curve, 

 and the values of the selected ordinates are thus readily 

 measured off. For analysis of valve-motions, of alter- 

 nating-current curves, of tidal observations, and diurnal 

 magnetic variations, the method presents _ certain 

 advantages, as it requires no multiplication of ordinates by 

 sines or cosines.— Prof. S. P. Thompson: Demonstration 



of the subjective nature of the difference tone. Two 

 tuning-forks of frequencies 332S and 3584 were sounded 

 loudly. On striking the second the difference tone was 

 heard, but while the notes from the two forks seemed to 

 come in a definite direction from an external source, the 

 difference tone seemed to be located in the ear itself. — 

 Sir George Greenhill : Spinning tops and gyroscopic 

 apparatus. A 52-inch Otto bicycle wheel was shown 

 mounted on an axle with ball bearings, and spun by hand 

 with the point in a small cup, to serve as a spinning top 

 visible to a large audience. The gyroscopic apparatus was 

 made of an ordinary 28-inch bicycle wheel, the axle 

 screwed into a stalk of a short length of rifle barrel, 

 suspended from a lug on a bicycle hub ; the hub is 

 fastened to an iron bracket, which is bolted to the under 

 side of a beam or sleeper, large enough to absorb vibra- 

 tion, and resting on two step ladders. The wheel is spun 

 by hand, and the axle is projected to obtain any desired 

 gyroscopic motion, undulating, looped, or with cusps. The 

 wheel can be detached by unscrewing the pin through the 

 lug, and can then be used like the large wheel as a 

 spinning top, or as the " Top on the top of a Top " 

 described in Maxwell's " Life." Put the wheel out of 

 balance by a bar through the spoke and hold the axle, and 

 it will serve as a pendulum, making oscillations however 

 large, or complete revolutions, and the effect may be in- 

 vestigated of varying the angle of the axle with the vertical. 

 — Prof. H. N. Allen : A model illustrating the passage of 

 a light wave through quartz. If a crystal is so cut, and 

 a wave sent through it in such a way as to avoid separa- 

 tion of the two component waves by double refraction, it 

 is easy to construct models showing how a vibration gradu- 

 ally alters in form as it passes through the crystal. The 

 model exhibited illustrates the passage of a wave originally 

 plane polarised through a crystal which rotates the plane 

 of polarisation of light sent along its axis (quartz). — Prof. 

 A. Anderson and J. E. Bowen : The measurement of 

 contact differences of potential. The paper describes two 

 methods of measuring the contact differences of potential 

 of pairs of metals. The first, or deflection, method 

 depends on the property which a radio-active source has 

 of destroying a field of electrostatic force in air, and the 

 second, or null, method on the possibility of determining 

 by means of such a source whether such a field exists 

 between two plates at zero potential. Measurements were 

 made on ten different metals, and it was found that both 

 methods gave practically the same results provided that 

 the time which was allowed to elapse between the two 

 measurements was sufficiently small. The addition law 

 was verified. — A. Johnstone : A short table of circular 

 and hyperbolic functions for complex values of the argu- 

 ment. 



Zoological Society, Tune 13.— Mr E. T. Newton, F.R.S., 

 in the chair. — H. G. Plimmer :» Report on the patho- 

 logical examination of rats caught in the Regent's Park 

 and in the society's gardens. Five hundred rats had been 

 examined between January 1 and May 17, all in a pre- 

 cisely similar manner. The spleen, lungs, glands, and 

 blood were examined microscopically, and from any animal 

 which looked in any way unhealthy cultures were made. 

 The results were summarised as follows :— 5 rats were 

 caught in the park, and 495 in the gardens; 283 of these 

 were males and 217 females. Three rats had tubercle, 

 10 had tapeworm cysts in the liver, 49 had Trypanosoma 

 lewisi in their blood, 2 had empyema (not tubercular), 

 I had a tumour of the lower jaw (the result of an old 

 injury), and i had pleuritis and hydrothorax (not tuber- 

 cular). Bacteria were found in 71 rats : in 40 in the lungs 

 and in 31 in the spleen. Saccharomycetes were found in 

 the lungs of 16 rats. Fleas were found on 4 rats, and 

 lice on 3 rats. The general condition of the rats was very 

 good, and in none was anything at all suspicious found. 

 —Dr. R. E. Drake-Brockman : Antelopes of the genera 

 Madoqua and Rhvnchotragus found in Somaliland. The 

 author made general remarks on all the dik-diks, and gave 

 a short account of the species and subspecies, includmg 

 the description of a new form.— Hon. Paul A. Mothuon : 

 An amphipod from the Transvaal. A detailed description 

 of a new fresh-water gammarid of the genus Eucrangonyx 

 found in caves in the Transvaal.— R. Uydokker : Three 

 African animals. The first specimen was the skull of a 



NO. 2174, VOL. 86] 



