March lo, 1881] 



NA TURE 



451 



the coils the shutter was deflected so as to close or partially close 

 the tube and shut off the beam of light. It will be understood that 

 when a ray of light fell on the cell and diminished its resistance, 

 the cun-ent in the coils would increase to a degree proportional to 

 tlie intensity of the ray, and thus the shutter would proportionally 

 cut off' the light in the receiver. If now a number of these 

 elementary circuits were combiafed so as to provide a mosaic of 

 cells to trausmit the reflected image of an object, and a screen 

 to receive the corresponding beams of light controlled by the 

 shutters at the other end of the line, there would be a means of 

 sending light and shade images by wire. A rapidly rotating 

 arm carrying a row of cells upon it might answer for a stationary 

 mosaic transmitter, and need fewer cells, while a Jajianese mirror 

 having its curvature altered by electromagnets behind might be 

 made to act as a receiver ; the "magic" images of that mirror 

 being due to inequalities of curv,ature. Prof. Ayrton agreed with 

 Mr. Bidwell in hi. conclusion that selenium cells of high resis- 

 tance were more sensitive to light than cells of low resistance. 

 Dr. Coflin suggested that Mr. Bidwell should adopt other than 

 the cylindrical form of receiver, and move an image of the 

 object across the pin-hole. Prof. G. C. Foster advised bringing 

 the light always on one and the same part of the selenium cell. 



Quekett Microscopical Club, February 25. — T. C. White, 

 president, in the chair. — Ten new Members were elected, and 

 numerous donations received. — A communication was made by 

 Mr. A. D. Michael, announcing the discovery by Mr. Beaulah 

 oi Myobia musculi upon a mole, this parasite having been pre- 

 viously regarded as one confined to mice. A discussion ensued 

 as to the frequent errors in classification and nomenclature 

 arising from insuflicient observation. — The Rev. J. E. Fase 

 exhibited and described a convenient form of grooving slide, 

 which could be used either with high- or low-power objectives. 



Institution of Civil Engineers, February 22. — Mr. Aber- 

 nethy, F. R.S.E., president, in the chair. — The paper read was 

 on the weight and limiting dimensions of girder bridges, by Mr. 

 M. am Ende, Assoc. M. Inst. C.E. 



Edinburgh 

 Royal Society, February 7. — Prof. Maclagan, vice-pre- 

 sident, in the chair. — After reading the obituary notices of Lord 

 Ormidale, Dr. .Sharpey, Mr. Lassell, and other deceased Fellows, 

 the chairman called on Prof. George Forbes to communicate his 

 paper on a simple and accurate method of determining the 

 longitude of a place by a single observer without the aid of any 

 instrument for measuring time. The method consisted in taking 

 advantage of the daily change in the moon's declination, which 

 for four or five days during each lunation was sufficiently rajiid 

 to be measured witli considerable accuracy by means of a sextant 

 and artificial horizon. The calculations and reductions were too 

 intricate to be effected save by a method of approximation and 

 interpolation such as that which the author had given in his 

 paper. — Mr. J. Y. Buchanan read a short paper from Prof. 

 Liversidge descriptive of a specimen of Stilbite that had been 

 brought by the Challenger from Kerguelen's Island. — ^Prof. J. 

 Blyth gave an interesting account of certain experiments vrhich 

 he had made with a simple form of selenium cell. Two ordinary 

 metal combs with every alternate tooth broken away were set 

 close together, so that each remaining tooth in either fitted with- 

 out touching into the interstice between two remaining teeth in 

 the other. The two combs were then brought into electrical 

 contact by the selenium, which was poured in between the teeth ; 

 and thus a selenium cell was formed with a large surface and 

 small resistance. In one special form of cell the combs were 

 bent round a glass tube, inside which a singing flame was set. 

 The accompanying rhythmic fluctuations in the luminosity of the 

 flame were reproduced as sound in the telephone receiver. The 

 difficulty of getting good selenium at the time induced the author 

 to try if amorphous phosphorus would serve as a substitute. A 

 "radial cell," in which the interstices between the dove-tailing 

 electrodes were filled with phosphorus, was found to be not 

 sensitive to light ; but such an arrangement was discovered to be 

 a battery in itself, giving rise to currents which varied with the 

 pressure that was brought to bear upon the phosphorus. This 

 property at once suggested a phosphorus cell as a possibly' useful 

 transmitter in a teleplionic circuit. Another curious effect was 

 noted, viz. that phosphorus under the action of a variable current 

 glowed with a beautifully varying phosphorescence. — Mr. Aitken 

 communicated further experiments on the formfttion of fogs. 

 His former experiments he had repeated at as low temperatures 

 as 8' F., invariably finding that in filtered air no fog formed. 



Discussing the production of dry fogs, i.e. fogs that are formed 

 in non-sal Hialdd air, tlie author pointed out that certain kinds of 

 fog-forming dust were much more efficient in their action than 

 others. Some, invirtueprobably of their deliquescent properties, 

 formed clouds in non-saturated air ; others only acted in satu- 

 rated air ; while a third class required the air to be super-saturated. 

 In connection w ith the change of state of moisture in the atmo- 

 sphere, Mr. Aitken explained the formation of the various forms 

 of ice-crystals by application of the principle that the slower the 

 crystallisation the more regular and simple it is. Hence complex 

 types of crystals betoken a rapid crystallisation. The paper 

 ended with a few instructive remarks upon liquid surface-tension 

 as an important factor in the gi'owth and coalescence of rain- 

 drops as they descend towards the earth. — Prof. Tait, in a short 

 note on thermal conductivity, intimated that he had solved the 

 equation for conduction, taking into account the temperature- 

 variations of the conductivity and specific heat. He further 

 pointed out that, at least in the case of iron, most of the decrease 

 with temperature that apparently takes place in the value of the 

 conductivity is in all likelihood referable at once to the change 

 in specific heat ; so that perhaps after all conductivity varies 

 very slightly indeed .with temperature, and is practically constant 

 through ordinary ranges. Prof. Tait also gave a simple experi- 

 mental illustration of the diminution in the surface-tension of 

 water produced by heating. A red-hot poker was held close 

 over a level water surface on which Lycopodium dust was 

 sprinkled, when at once the dust was drawn away to cooler 

 regions as if violently repelled by the strongly-heated metal. — 

 Dr. Haycraft communicated a paper in which he show ed that 

 the hepatic cells of man and other domestic animals, several of 

 which he had examined, are possessed of true cell-walls. These 

 may be demonstrated by placing a few scrapings from a fresh 

 organ on a slide, and pressing the cover-glass down so as to 

 crush them. The membranes are then to be seen projecting 

 from the half-broken cells, or scattered about the preparation. 



Boston, M.\ss., U.S.A. 

 American Academy of Arts and Sciences, February 9. — 

 The president. Prof. J. Lovering, in the chair. — Prof. H. P. 

 Bowditch presented some observations on the senses of sight 

 and touch. An observer having noticed the position of a point 

 at the centre of a target, shut his eyes, and after a measured in- 

 terval of time attempted to touch this point again. It was found 

 that the attempts were more successful when two seconds had 

 elapsed than in tlie cases when more or less time had intervened. 

 — Mr. N. D. C. Hodges read a paper upon the thermodynamic 

 basis for the kinetic theory of gases. By means of the funda- 

 mental equations of thermodynamics the mathematical analysis 

 of the kinetic theory results at once ; and an expression is ob- 

 tained for the absolute mass of a molecule. — Prof. Pickering, 

 in a paper on variable stars, discussed their changes in brilliancy 

 and grouped them according to a new law. — Mr. Arthur Searle 

 gave some of the results of his observations on the zodiacal 

 light. — Mr. Harold Whiting, in an abstract of a forthcoming 

 paper, stated that he had found the rate of propagation of what 

 may be called the magnetic wave to vary from 30 feet to 300 

 feet per second. — Prof. Goss presented some observations on 

 the strength of fir beams. 



Pai^is 

 Academy of Sciences, February 21. — M. Wurtz in the 

 chair. — The following papers were read : — Meridian observa- 

 tions of small planets at Greenwich and Paris Observatories 

 during the fourtlr quarter of 1S80, communicated by M. Mouchez. 

 — On the parallax of the sun, by M. Faye. He indicates in a 

 table nine methods of determining the earth's distance from the 

 sun. He holds that the method of physicists is best ; that the 

 sun's parallax, S"'Sl3, is now determined by them to within y^ 

 of a second ; and that the seven astronomical methods converge 

 more and more towards this result, and tend to confirm it, with- 

 out having equal certainty. — Male eels, compared with the 

 females, by M. Robin. — General considerations on the Crus- 

 tacean fauna of great depths in the Carribbean Sea and the Gulf 

 of Mexico, by M. Alph. Milne-Edwards. This deals w ith some 

 results of the cruises in the Blake. Many new Crustacean species 

 were obtained, and certain groups previously thought foreign to 

 American waters were found abundantly at great depths. Ano- 

 mouran and macrouran Crastacea there abound. Numerous forms 

 intermediate between groups that have been thought very 

 distinct are discovered (and the author cites several examples). 

 — New clinical researches tending to prove that the cerebellum 



