33° 



NATURE 



\_Atigust 5, 1880 



condition of the Society. Tlie address of the president, Mr. T. 

 Southwell is on the Extinction of Native Races. Among other 

 papers of interest are: "Notes on Collecting Lepidoptera in 

 Norfolk, 1878," by Mr. F. D. Wheeler; "Discovery of Remains 

 of Emys bttaria in the Mundesley River-bed," by Mr. H. E. 

 Woodward ; The Bird-Life and the Geology of the Shiant 

 Isles, by Mr. -Ilarvie-Brown and Prof. Heddle respectively ; 

 Notes on Hawking in Norfolk, by Prof. Newton and Mr. ]. 

 E. Ilarting ; Ornithological Notes and Meteorological Obser- 

 vations. 



The Proceedings of the Liverpool Naturalists Field Club for 

 1879-80 contains notes of the excursions and meetings of the 

 Society. The only papers given are by the president, the Rev. 

 H. H. Higgins, one being "Biographical Sketches in Zoology, 

 fi-om its Origin to its Union with Botany in the Science of 

 Biology. " 



The additions to the Zoological Society's Gardens during the 

 past week include a Macaque Monkey {Macacus cynomolgus) 

 from India, presented by Mr. J. Anson ; a Side-Striped Jackal 

 (Cam's lateralis) from East Africa, presented by Commander 

 Owen, R.M.S. Anglian ; aCommon Ocelot (Felis pardalis) from 

 Mexico, presented by Mr. A. L. Schiitte ; two Common Pea- 

 fowls (Favo cristata) from India, presented by Mrs. Joseph 

 Hoare ; four Globose Curassows (Crax glohicei'a), a Little Guan 

 [Ortalida motmot) from British Honduras, presented by Mr. F. 

 P. Barlee, CM. G. ; ten Amaduvade Finches (Estrelda aman- 

 dava) from India, presented by Mr. J. W. Wilson ; a Mississippi 

 Alligator (Alligalor mississippiensis) from North America, pre- 

 sented by Mr. T. L. M. Rose ; two Horrid Rattlesnakes [Cro- 

 talus horriJus) from Nicaragua, presented by Messrs. Holt, 

 Lord, and Co. ; an Anaconda (Eiincctes murinits) from South 

 America, presented by Mr. G. H. Hawtayne; a Bonnet Monkey 

 [Macacus radintus) from India, an Arctic Fox (Catiis lagopus) 

 from the Arctic regions ; a Nilotic Crocodile (Crocodilus vul- 

 garis) from Africa, deposited ; a Nylghaie [Boselaphtts pictus) 

 from India, a Collared Peccary {Dicolyles tajcicu) from South 

 America, two Common Otters {Lutra viilgai-is, jv.), British ; a 

 Ground Hornbill {Bucorvus abyssinictis), an Elate Hombill 

 [Buceros clalus) from West Africa, a Virginian Eagle Owl (Bubo 

 virginiamts) " from North America, a White-necked Crow 

 (Corvus scapulalus) from Africa, purchased; a iCoUared Fruit 

 Bat (Cynonycteris collaris), born in the Gardens. 



ON CURRENTS PRODUCED BY FRICTION 

 BETWEEN CONDUCTING SUBSTANCES, 

 AND ON A NEW FORM OF TELEPHONE 

 RECEIVERS 



T N a communication to the Royal Society of Edinburgh of date 

 -*■ January 6, 1879, I showed that "electric currents were 

 produced by the mere friction between conducting substances." 

 The existence of these currents can be easily demonstrated either 

 by a telephone or a Thomson's galvanometer. I have since 

 found that these currents are, for all pairs of metals which I have 

 yet tried, in the same direction as the thermo-electric current 

 got by heating the junction of the same two metals. They are 

 also, approximately at least, stronger in proportion as the metals 

 rubbed are far apart on the thermo-electric scale — the strongest 

 current, as far as I have yet observed, being got by rubbing 

 antimony and bismuth together. These observations clearly 

 point to a thermoelectric origin for the currents; but it is 

 possible that they may be due partly to the currents suggested 

 by Sir William Thomson as the cause of friction, and partly, 

 also, to contact force between films of air or oxide adhering to 

 the surfaces of the metals. 



Having ascertained that these friction-cuiTents are of some 

 strength and fairly constant, I proceeded to make several kinds 

 of machine for producing currents on this principle. One of 

 them consists of a cylinder of antimony, which can be rotated 

 rapidly, while a plate of bismuth is pressed hard against it by a 



' Abstract of a paper read before the Royal Society of Edinburgh by 

 James BIyth, M.A., F.R.S.E., on May 3, 1880. 



stiff spring. When this machine is included in the same circuit 

 w ith a microphone and a Bell telephone, the current got from it 

 is quite sufficient to serve for the transmission of musical sounds 

 and also loud speaking. The transmitter, which I have found 

 most fer\iceable in my experiments, is made by screwing two 

 smalt cubes of gas-carbon to a violin, and placing between 

 them a long stick of carbon pointed at both ends, the points 

 being made to rest in conical holes in the carbon cubes. The 

 looseness of the contact is regulated by a paper spring. This 

 forms an excellent and handy trasmitter for all kinds of musical 

 sounds, and also serves very well for transmitting speech. 



Seeing that friction between metals clearly produces a current, 

 it seemed natural to inquire if the converse held good, that is, 

 il a current from a battery sent across the junction of two metals 

 affected the friction of the one upon the other. I have tested 

 for this in a variety of ways, and the results obtained leave me 

 in doubt whether to attribute them to variations in the friction, 

 or to actnal sticking produced by fusion of the points of contact 

 through which the current passes. The most noticeable effect is 

 produced when one of the rubbing bodies is a mere point, and 

 the other a smooth surface of metal. This led me to make a 

 modification of the loud-speaking telephone of Mr. Edison, in 

 order to get audible indications of changes of friction produced 

 by the passing of a variable current. It consists of a cylinder 

 of bismuth accurately turned and revolving on centres. The 

 rubbing-point is made of a sewing-needle w ith its point bent at 

 right angles, and its other end attached to the centre of the 

 mica disk of a phonograph mouthpiece. It is evident that this 

 is only a loose contact, which can be perpetually changed. 

 When this apparatus is included in the circuit with the violin- 

 microphone and three or four Bunsen cells, the violin sounds, 

 as wg^ to be expected, are heard proceeding from the loose- 

 contact, even when the cylinder is not rotated. They are in- 

 creased, however, in a remarkable degree by rotating the 

 cylinder slowly, so much so that a tune played on the violin can, 

 with proper care, be di^inctly heard all over an ordinary room. 



With regard to the explanation of this effect, it is evident, that 

 electrolysis can in no sense come into play, as is supposed to be 

 the case in Edison's instrument. I am inclined to look for the 

 explanation rather in the direction of the Trevelyan rocker, 

 although the circumstances are considerably difterent in the two 

 cases. In the rocker we have the heat passing from a mass of 

 hot metal through two points of support to a cold block, where- 

 as, in the other case, the heat is only intense at the points of 

 contact, the rest of the metals being comparatively unaffected. 

 The variations in the current produced by the transmitting 

 microphone must cause corresponding variations in the heat at 

 the point of contact of the needle with the cylinder, and this 

 again produces a mechanical movement of the pressing point, as 

 well as of the air surrounding it, sufficient to give forth sound- 

 waves. If such be the case the effect should be different for 

 different metals, those answering best which have the lowest 

 tliermal conductivity and also the lowest specific heat. That this 

 is really so is shown by substituting cylinders of other metals for 

 the bismuth, all other things remaining the same. In this way 

 I have compared lead, tin, iron, copper, carbon, and find that 

 they all give forth the simple loose contact-sound when the 

 cylinder is stationary, but that it is only with bismuth that 

 there is any very great intensification of the sound when the 

 cylinder is rotated. Now, by consulting the appropriate tables 

 I find that bismuth is a fraction lower than any other common 

 metal in specific heat, while it is much below them all in thermal 

 conductivity. This seems to bear out my explanation to a 

 certain extent. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 

 Cambridge. — The subject for the Sedgwick Prize essay, 1SS3, 

 is "The Classification of the Cambrian and Silurian Rocks." 

 The prize is open to all graduates of the University of Cambridge 

 \\ho have resided sixty days during the twelve months preceding 

 October I, 1SS2. The essays must be sent in to the Registrary 

 on or before October I, 1SS2. 



^ SCIENTIFIC SERIALS 



Proceedings of the Academy of Natural Sciences of Phila- 

 delphia. Part I, January to April.— Thomas Meehan, on 

 disarticulating branches in Ampelopsis (the annual growth is dis 



