68 



NATURE 



[Nov. 21, 1878 



F, von Miiller and L. Rummel. The authors have prepared 

 alstonin from the bark of alstonia constricta, and duboisin from 

 the leaves and twigs of duboisia myoporoides ; the latter closely 

 resembles piturin, — On the determination of lithia by phosphate 

 of soda, by C. Rammelsberg. The author confirms his previous 

 results as to the formation of a double salt of sodium and lithium 

 phosphate and the consequent inaccuracy in lithia determina- 

 tions made by Mayer's method j he also gives some analyses of 

 lithia micas. 



Physical Society, November 9. — Prof. G. C. Foster, vice- 

 president, and aftenvards Prof. W. G. Adams, president, in th- 

 chair. — The following candidate was elected a Member of the 

 Society : — Sir Frederick Elliot. — Prof. W. G. Adams explained 

 a simple appliance made by Mr. S. C. Tisley for exhibiting 

 the coloured bands due to interference with thick plates. The 

 bands due to regular reflection and refraction were produced by 

 two thick plates nearly parallel to each other and fixed in a brass 

 box with rectangular apertures on its flat faces so that the light 

 fell on the first plate at an angle of 60°, the whole apparatus being 

 of a convenient size for the waistcoat pocket. On a previous 

 occasion (June 23, 1877), Prof. Adams exhibited these bands to 

 the Society, but not in a portable form. The elliptical interfer- 

 ence bands, due to the scattering or diffusion of light at a point 

 on the front surface of one of the plates, were shown by means of 

 a precisely analogous arrangement, except that the inclination of 

 the plates to each other was somewhat greater ; in this case the 

 interference bands, formed by r<?^/rtr reflection and refraction, fall 

 in another direction, so that they are not received by the eye ; the 

 diffusion interference fringes obtained were clearly visible when 

 thrown on the screen. They are formed by rays once diffused 

 from points on the first surface and afterwards regularly re- 

 flected and refracted from the front and back faces of the two 

 plates in succession. Prof Adams pointed out that this instru- 

 ment would form a convenient means of obtaining polarized light 

 in cases where the length of a Nicol's prism is objectionable, 

 for instance, under the stage of a microscope ; the light will 

 be completely polarized if the plates be placed to receive the 

 light at the polarizing angle, and the field will be much brighter 

 than when a plate of tourmaline is employed. — Prof. W. F. 

 Barrett exhibited and explained Edison's microtasimeter and 

 carbon telephone. These have been recently described in 

 Nature. In the course of a brief recapitulation of the history 

 of these instruments, he referred to Du Moncel's early observa- 

 tions, published in 1856, that variations in the resistance of a 

 circuit can be produced by varying the pressure on metallic 

 surfaces in contact, and after referring to Clerac's plumbago 

 rheostats he stated that Edison was probably the first to apply 

 the diminished resistance of carbon under pressure to a practical 

 use, which he did early in 1877 in his carbon relay, the pro- 

 genitor of the carbon rheostat, micro-tasimeter and carbon tele- 

 phone. In all he uses compressed lampblack, a button of which 

 may be formed as follows. The wick of a paraffin lamp having 

 been cut so that it smokes, a quantity of lampblack is formed in 

 the chimney ; the lower portion, which has the more intense black 

 colour, is collected from time to time, and all brown particles 

 must be carefully removed, since they offer a greater resistance. 

 The mass is compressed into a disc about the size of a sixpence, 

 crushed, passed through a fine sieve, and again compressed, and 

 this operation may be two or three times repeated in order to attain 

 to perfect uniformity. The original form of tasimeter, in which 

 the hard rubber or other substance was placed horizontally, has 

 been modified so that the whole is vertical. The carbon button 

 rests on a smooth metallic surface in connection with a binding 

 screw, and a similar conducting surface rests upon it leading to 

 a second binding screw. A strip of hard rubber i inch long, 

 \ inch wide, and y\ inch thick, is supported vertically above it, 

 its upper end being attached to a fine screw worked by a tangent 

 screw with graduated head. The whole is inclosed in a heavy 

 conical brass box. Prof. Barrett suggested that it would be pre- 

 ferable to make this jacket cylindrical, and that the whole should 

 be inverted, because the weight of the strip on the button is 

 found to prevent the needle of the galvanometer returning at 

 once to zero. Employing one Daniell's cell and inserting a 

 shunt, Wheatstone's bridge, and resistance coils in the circuit, 

 it was shown that the hand, at some distance, caused a consider- 

 able deflection, and Prof. Barrett stated that in a still room the 

 instrument becomes so sensitive as to be almost unmanageable. 

 By replacing the hard rubber by a strip of gelatine varnished on 

 one side, a very slight change in the hygrometric state of the 

 atmosphere can be detected by the absorption of moisture 



causing expansion of the gelatine, and, therefore, compression 



of the carbon. Its action as an aneroid baroscope was su^crested 



by Prof. Barrett, the button being associated with an exhausted 



box. He pointed out that before the tasimeter can be used as 



a measuring instrument, experiments must be made in order to 



ascertain the exact relation between the resistance of carbon and 



the pressure to which it is subjected. The carbon telephone, full 



particulars of which will be found in Nature, vol. xix. 



p. 12, was next described, and Mr, Adams, Mr, Edison's 



assistant, now in England, exhibited a complete transmitting 



apparatus, with call, &c. A very ingenious and simple form of 



shunt, received from Mr. Edison with the tasimeter, deserves 



mention, A row of brass studs fixed on a board are united by 



plugs, so that if the current enters at one end it can pass out at 



the other without meeting with any appreciable resistance. But 



if a plug be removed it throws in about 4 inches of a resisting 



wire wound over two rows of pins, underneath the board, one 



row of which is in metallic connection with the studs ; thus the 



entire length of wire is in circuit when all the plugs are removed. 



Finally, Prof. Barrett mentioned that a communication has just 



been received from Mr. Edison stating that he has succeeded in 



arranging an efficient receiving instrument in which no form of 



magnet is employed. — Mr. Ladd then showed several forms of 



electric lamp arranged so as to render the use of clockwork 



unnecessary. In that known as Wallace's workshop lamp the 



spark passes between the edges of two plates, the lower one 



being fixed while the upper one is raised to a suitable distance by 



an electro-magnet brought into action immediately on the passing 



of the current. A second form, in which an annular magnet 



was employed, acted on the same principle, the armature carrying 



the upper plate being specially arranged so as to give a maximum 



of attractive force. In the third form, the V-lamp, two rods of 



graphite were inclined at an angle of 45° to the vertical, resting in 



contact on a piece of china. Immediately on the current passing 



an electro-magnet is caused to act, and, after the rods have been 



firmly gripped, they are separated and the support removed. 



Should the circuit be broken they will at once fall together. 



VlENN.\ 



Imperial Academy of Sciences, October 10, — The deaths 

 of Dr. Rokitansky and Prof, Tomaschek were referred to, — The 

 following among other papers were read : — The dolomite ridges of 

 South Tyrol and Venetia (Heft 2 and 3), by Dr. Mojsisovics. — 

 On electric penetration of glass, by Prof. Alach. — On the relation 

 of diffusion-phenomena to the second proposition of the mechani- 

 cal theory of heat, by Prof. Boltzmann. — Calorimetric research 

 on the heat of combination of carbonic acid gas and ammonia 

 gas, to carbonate of ammonia, by Herr Lecher. — Action of 

 radiant heat of the sun on a body in shade — time of occurrence of 

 maximum temperature, by Herr Schlemiiller. — Description of 

 a telescope, by means of* which, with one objective, you may 

 point on two objects simultaneously, one distant, the other near, 

 (sealed packet) by Herr Schneider. — Physical experiments, by 

 Dr. Gross. — Distance reflector with precision-reading, by Herr 

 Kuczera. — Discovery of a comet, by Mr. L. Swift. — Meteorite 

 fall at Tieschitz in Miihren, July 15 last year, by Herr Tscher- 

 mak, — Development-history of the prothallium of Scolopendrium 

 vulgare, Sym., by Dr, Beck. 



CONTENTS Pagr 



Mathematics at Cambridge 49 



"Cram" Books 51 



Letters to the Editor:— 



The Divisibility of the Electric Light. — William Trant .... 52 



Duplexing the Atlantic Cable. — Herbert Taylor 52 



Remarkable Colour- Variation in Lizards. — Prof. A, Leith Adams, 



F.R.S.; J. Wood-Mason S3 



The Drought. — Hyde Clarke 53 



Sewerage and Drainage. — Alfred S. Jones 53. 



Rayons du Crepuscule. — Miss Annie Lev . . 54 



The Power of Stupefying Spiders Possessed by Wasps.— Henry 



Cecil S4 



The Ayrshire Crannog.— Dr. Robert Munro 54 



On the Utilisation of the African Elephant. By Sir J. FaVRER, 



F.R.S 5+ 



Synchronised Clocks {With Illustrations) 55 



The Telephone, its History, and its Recent Improvements, III. 



By Prof. W. F. Barrett (With Illustrations^ 56 



Notes 5& 



Charles AdolpheWurtz 62 



On the Constitution of Matter in the Gaseots State . . . , 62 



University and Educational Intelligence 65 



Scientific Serials 66 



Societies and Acadeviies . , 67 



