August 25, 1881] 



NAIURE 



387 



visitors had been either medical men, architects, or engineers. 

 The representatives of the exhibitors, who have been in daily 

 attendance during the Exhibition, marked their appreciation of 

 the arrangements u;ade for their convenience by presenting on 

 Saturday a small purse of gold to the superintendent, Mr. 

 Smithson. The closing of the Exhibition was taken advantage 

 of by the St. John Ambulance Association to give a demonstra- 

 tion of ambulance practice, and during the afternoon a large 

 number of the vi-itors assembled in the conservatory to witness 

 the practice, which was conducted by Major Duncan, Mr. 

 Cantlie of Charing Cross Hospital, Mr. Furley, Dr. Crook- 

 shank, and Surgeon-major Baker. Prizes were competed for by 

 squads of the Grenadier Guards, the Finsbury Rifles, and the 

 Metropolitan Police. Mr. John Eric Erichsen (the chairman). 

 Dr. Poore, Dr. Steele, Mr. George Godwin, Mr. Rogers Field, 

 and other members of the Exhibition Committee were present 

 during the day. It is expected tliat the prizes which have been 

 awarded will be distributed at tlie Annual Meeting of the Parkes 

 Museum in the autumn. 



The additions to the Zoological Society's Gardens during the 

 past week include a Ring-tailed Lemur (Lemur catta) from 

 Madagascar, presented by Mr. E. O. Brookfield ; a White- 

 collared Mangabey (Cercocebus collaris) from West Africa, pre- 

 sented by Mr. James Jameson; a Diana Monkey {Cercopithecus 

 (iiaiia) from West Africa, presented by Mr. Louis Wyatt ; a 

 Macaque Monkey [Macaciis cynomolgus) from India, presented 

 by Mr. R. Edge ; two Vulpine Phalangers (PAalant^ista vulpina) 

 from Australia, presented by Mr. George White ; a Lesser Sul- 

 phur-crested Cockatoo [Cacatua sulphurea) from the Moluccas, 

 presented by Mrs. Beard ; two Wonga-wonga Pigeons (La(CO- 

 sarcia picata) from New South Wales, presented by Mr. J. 

 Burnham ; a Royal Python (Python regiiis) from West Africa, 

 presented by Mr. G. H. Garrett ; a Grey Parrot {/'si/tacus eri- 

 thaciis) from West Africa, deposited ; a Lesser White-nosed 

 Monkey {Cercapithcctis pelaiirisia), two Pluto Monkeys (Cerco' 

 pilhecus pliito] from West Africa, purchased ; a Zebu (Bos 

 indicus), a Pampas Deer (Cariacus campeslris), born in the 

 Gardens. Among-t the additions to the Insectarium during the 

 past week are pupce of Attacus attrota (one of which has since 

 emerged) and Ceratocampa ixion, from Brazil ; larvte of the 

 Madder Hawk-Moth (Deilephila galii), the Death's-head Hawk- 

 Moth (Acheroiilia atropos), the Poplar Hawk-Moth (Smeriiithus 

 populi), and Fox Moth (Bombyx riibi), and perfect insects of the 

 Water Stick-insect (Ranatra linearis). 



PHYSICAL NOTES 



M. Samuel, of Ghent, has brought before the Belgium 

 Academy a method of registering telegraphic signals received 

 through the mirror galvanometer (£■«//., No. 5). On the screen 

 receiving the light are fixed two selenium elements, one to the 

 right, the otlier to the left. When either is illuminated its 

 conductivity of course increases, and it acts as a relay on an 

 electro-magnet, which causes a Morse dot or dash to be marked 

 on paper. There are tv\'o local batteries, one having I wo cir- 

 cuit-, which pass through the selenium pieces and the electro- 

 magnets, while the other is for the electro-chemical writing. In 

 this latter, a band of piper saturated with iodide of potassium 

 passes continuously over a small copper cylinder which is con- 

 nected with one pole of the second battery. Above the paper 

 are the ends of the armatures of the electro-magnets ; to one is 

 attached a vertical platinum rod, to the other a small triangle 

 with platinum base (horizontal). The rod and triangle are con- 

 nected, through the armatures, with the other pole of the second 

 battery, and they press the paper band on the cylinder each time 

 the armatures are attracted, giving a dot or a dash as the case 

 may be. The dashes, instead of being longitudinal, are at right 

 angles to the length. If the ordinary lamp of the galvanometer 

 be replaced by sunlight or hme-light, the electro-magnets (M. 

 Samuel points out) may be actuated directly without use of a 

 galvanometer relay ; Bell's selenium elements having an average 



resistance of only 150 ohms in sunlight, and 300 ohms in 

 darkness. 



An evaporimeter with constant level has been recently de- 

 scribed by Prof Fomioni (Reale 1st. Lomb., vol. xiv. fasc. x.-xi). 

 It consists of an oblong wooden case with a brass spiral descend- 

 ing into it from a micrometric screw. The spiral carries at its 

 lower end a small glass vessel which acts as feeder. A glass 

 siphon extends outwards horizontally from the feeder, and has at 

 its outer end a small cup, in which the evaporation takes place. 

 As the water evaporates in the cup the feeder is lightened, and 

 rises by action of the spiral, thus keeping the level constant. A 

 fine layer of oil in the feeder prevents evaporation from its 

 water-surface. There are guides to control the vertical move- 

 ments of the feeder, which, moreover, are indicated by means of 

 a weighted thread, affecting an external index on a disk. The 

 graduation of the instrument is expressed in millimetres of the 

 height of water in the evaporating vessel, 



SiGNOR Mauri (Riv. Set. Inst. No. 11) obtains an economi- 

 cal and very compact battery carbon, intimately united with the 

 electrode, as follows : — Finely-powdered graphite is mixed with 

 an equal weight of sulphur (which should be free from carbonates), 

 and the mixture is heated in an iron vessel until complete fusion 

 of the sulphur. The temperature should not be raised beyond 

 200°. When the mass is fluid it is poured into a suitable metal- 

 lic mould, and a thick copper w ire, bent zigzag, is quickly in- 

 serted, a part being left projecting. The mass is let cool slowly: 

 then it is easily drawn from the mould and is ready for use. 

 These carbons have a conductivity practically equal to that of 

 retort carbon, and are more electro-negative, consequently better 

 adapted for electromotive force. Coke-powder cannot be sub- 

 stituted for graphite, because it has too little conducting power. 

 By increasing the proportion of sulphur, the resistance may be 

 increased at will, and strong resistances may be thus easily pre- 

 pared in place of resistance-coils of copper wire. (S. Mauri 

 further indicates a way of utilising graphite in construction of a 

 miner's fuse.) 



Repeating Mercadier's experiments in which an intermittent 

 beam meets smoked a surface within a glass tube containing 

 aqueous or ammoniacal vapour, and furnished with an ear-tube. 

 Prof. Mugna lately [Riv. .SVi. /W. No. n) made the effects 

 much better heard by attaching a small microphone to an elastic 

 membrane closing the tube ; and it was possible to operate at 

 such distance from the interrupting apparatus, that its noise was 

 no longer disturbing. Prof. Mugna further experimented by 

 suspending horizontally from a cocoon-fibre, within a glass case, 

 a short fine glass rod, with terminal lamina- of card or glass, or 

 very fine metallic foil. An intermittent beam sent against one 

 of the laminx when they were in a position parallel to the wheel 

 drove the system round in direction of the beam, indicating 

 (the author considers) a direct action of the latter. An air- 

 current due to thermal action should produce the opposite 

 motion. Besides, the phenomenon is still better when the air is 

 rarefied. 



In a note to the Vienna Academy, Dr. Margules calls atten- 

 tion to the beautiful figures that are produced in glycerine, when 

 the liquid is moved in a regular way, by rotation of a disk in 

 contact with it. These figures afford an insight into the form 

 of the surfaces and paths of the currents. They are due to the 

 water contained in the glycerine. 



The method described by Herren KirchhofT and Hahnemann 

 last year for determining the heat-conductivity of metals, has 

 been applied by them ( IVieJ. Ann., No. 7) to three varieties of 

 iron, and to lead, tin, zinc, and copper ; and the electric con- . 

 ductivity of these metals has also been measured. The conclu- 

 sion is that the ratio of these conductivities is in general constant 

 in these different metals, with exception of iron, and it is thought 

 the exception may be connected with magnetic properties. Herr 

 H. F, Weber's result disagrees with this, for he finds the ratio 

 to be a linear function of the product of specific heat and 

 density. The authors are unable to discover the cause of this 

 discrepance. 



An initial attempt to elucidate the ratio of the specific heat of 

 liquid organic compounds to their composition has been made 

 by Herr von Reis ( ll-'ieii. Ann., No. 7). It appears from his 

 researches that the diflference of the molecular heat of homologous 

 compounds at 20' boiling point, and from 20° to 100°, is very 

 regular : in the former case it is S'o and in the latter 7 '5. 



