ya7i. 6. 



NATURE 



235 



It was found that the second form of experiment gave the 

 most uniform results ; the method by cooling being less accurate, 

 owing to currents of air in the room, &c. 



The results are embodied in the following Table : — 



(Rate of Heating from 25° to 50°) 



There are two ways in which heat can get from the gla^^s globe 

 to the thermometer — (i) By radiation across the intervening 

 space ; (2) by communicating an increase of motion to the mole- 

 cules of the gas, which carry it to the thermometer. It is quite 

 conceivable thnt a considerable part, especially in the case of 

 heat of low refran^ribility, may be transferred by "carriage," as 

 I will call it to di-tiMi;ui-.h it from convection which is different, 

 and yet that we sh uld not perceive much diminution of trans- 

 ference, and conequeiitly much diminution of rate of rise with 

 ' M = millionth of an atmosphere. 



increased exhaustion, so long as we work with ordinary exhaus- 

 tions up to I millim. or so. For if, on the one hand, there are 

 fewer molecules impinging on the warm body (h liich is adverse 

 to the carriage of heat), yet on the other the mean length of path 

 between collisions is increased, so that the augmented motion is 

 carried further. The number of steps by which the temperature 

 passes from the warmer to the cooler body is diminished, and 

 accordingly the value of each step is increased. Hence the 

 increase in the difference of velocity before and after impact 

 may make up for the diminution in tlie nuiiber of molecules 

 imjiinging. It is therefore conceivable that it may not be till 

 such high exhaustions are reached that the mean length of path 

 between collisions becomes comjiarable with the diameter of the 

 ca-e, that further exhaustion produces a notable fall in the rate at 

 v^hich heat is conveyed from the case to the thermometer. 



The above experiments show that there is a notable fall, a 

 reduction of pressure from 5 M. to 2 M. producing twice as much 

 fall in the ra'e as is obtained by the whole exhaustion from 760 

 millims. to i millim. We may legitimately infer that each 

 additional diminution of a millionth would produce a still greater 

 retardation of cooling, so that in such vacua as exist in planetary 

 space the loss of heat — which in that case would only take place 

 by radiation — would be exceedingly slow. 



SCIENTIFIC SERIALS 



Journal de Physique, December, 1 880. — Note on magic 

 mirrors, by M. Bertin. — On some applications of articulated 

 systems, by IVI. Robin. — Experiments on the discharge in rare- 

 fied gases, by M. Kighi. — Notice on tlie life and works of M. 

 Almeida. 



Archives des Sciences Physiques et h'aturclles, November 15. 

 —Meteorological ?•<?«<?«£' of the year 1879 for Geneva and the 

 Great St. Bernard, by M. Piantamour. — Disinfection of vehicles, 

 plants, collections of natural history, and various objects with 

 anhydrous sulphurous acid, by Dr. Fatio — Observations on a 

 memoir of M. Schonn, by M. Soret. — On the phenomenon of 

 hydration in peptonisation of albuminoid substances, by Dr. 

 Danilew.sky. — Notes on the winds of mountains, by M. Pittier. 

 — Case of diplopia, by Prof. Wartmann, &c. 



Reale Istituto Lombardo di Scieme e Lettere. Rendiconti. 

 vol. xiii. fasc. xviii., November, 1880. — This number contains 

 lists of prizes awarded and offered. 



Alii delta R. Accadeviia dei Lined, vol. v. fasc. I (December 

 5, 18S0). — New studies on the nature of malaria, by SS. Cuboni 

 and Marchiafava. — Graphic determination of the elastic force 

 relative to plane elements passing through a point, by .S. Modi- 

 gliano. — On the geological natureof strata met witli in the tubular 

 foundations of the new iron bridge built on the Tiber alRipa,tta, 

 and on the Unio siiuialus, Lamk., there found, by S. Meli. — 

 On the structure of the envelope of the ova of some fishes, by 

 S. Lep iri. — On the preservation of man in countries of malaria, 

 by S. Tommasi-Crudeli.— On bilinear ternary forms, by S. 

 Battaglini. — On the projected stations for systematic physical 

 observations in polar regions, by S. Cora. — On a cebocephalic 

 caprine monster, by S. de Sanctis. — On the recent restoration of 

 the scholastic and tomistic philosophy, by S. Ferri. 



SOCIETIES AND ACADEMIES 

 London 

 Photographic Society, December 14, 1880. — J. Glaisher, 

 F.R.S., president, inthechair.— Papers were read byProf.T. E. 

 Thorpe, F.R.S., on a simple and expeditious method of pre- 

 paring pyrogallol for dry plate development. The method 

 proposed is to put dry gallic acid and glycerine into a flask, 

 which is then heated to 200° on a sand tray, as long as bubbles 

 of carbon dioxide are seen to be formed in the liquid. The 

 gallic acid soon dissolves and is entirely converted into the 

 theoretical quantity of pyrogallol, viz., 80 per cent. — By Capt. 

 Abney, R.E., F.R.S., iodide and ammonia in gelatine emul- 

 sions. It was stated that iodides in gelatine bromide emulsion 

 kept the silver salts from being deposited upon the shadows, as 

 also that there is freedom from decomposition of the film, 

 and tendency to red fog, and more light can be used in preparing 

 and developing the plates.— And also by Capt. Abney on a 

 photographic sunshine recorder. This consisted of a semi-cylin- 

 drical box with a flat lid, in the centre of which is a small hole ; 

 round the inside of the cylinder strips of sensitive paper are 



