V. ABSORPTION. 233 



distance from the lower one. Through the upper cone a current of warm 

 water or steam is passed. Between the bases of the cones is introduced the 

 liquid whose thermal resistance is to be measured. 



1062. Apparatus used in researches on the Absorption 

 of Radiant Heat by gases and vapours. 



Professor Tyndall, F.R.8. 

 Phil. Trans., 1861. 



1065. A pair of concave Reflectors of Prima German 

 silver, 500 mm. in diameter, on brass stands, with supports for 

 carbon and tinder, for experiments on radiant heat. 



Warmbrunn, Quilitz, and Co., Rcrlin. 



1066. Melloni's Apparatus for investigating the laws of 

 radiant heat. H. Lloyd, Trinity College, Dublin. 



1072. Fouillet's Actinometer, for sidereal radiation. 



Conservatoire des Arts et Metier 's, Paris. 



1072a. Actinometer, for measuring the intensity of 

 Solar Radiation. /. Louis Sorct, Geneva. 



It is composed of a tube, of the diameter of about 35 millimetres, closed at 

 one end, and blackened inside. The end, which can be opened by removing 

 the stopper, is furnished with a diaphragm. The central tube is encircled with 

 a concentric brass wrapper, which has to be filled up with pounded ice, or with 

 snow. The apparatus is upheld by a horizontal axle upon a wooden support. 

 This axle is formed of a tube which, on one side, lets out the rod of the ther- 

 mometer (lacquered and blackened), and on the other may be adjusted to an 

 air-exhausting pump. The apparatus is directed towards the sun ; the orien- 

 tation is obtained by means of the exterior appendiculse. 



See Kecherches sur 1'intensite calorifique de la radiation solaire. Comptes 

 Rendus de 1' Association Fra^aise pour PAvancement des Sciences," 1st 

 Session, Bordeaux, p. 282. 



lO72b. Actinometer. 



M. Desains, Member of the Institute, Paris. 



1073. Fouillet's Pyrheliometer, for observations on solar 

 heat. Conservatoire des Arts et Metiers, Paris. 



V. ABSORPTION. 



1084. Ice-making Machine ; system of Raoul Pictet, & Co. 

 Raoul Pictet, fy Co., Geneva. Geneva Association for 

 constructing Scientific Instruments. 



This machine manufactures ice by means of anhydrous sulphurous acid. 

 This substance has the following advantages ^ 



1 . It is without action upon metals and fatty substances. 



2. It gives but slight pressures, never exceeding 4 atmospheres in a 



temperature of 30 centigrade. 



