Chemical Science. 385 



mined. He observes, that the same means of observation may be 

 applied to the study of the physical constitution of the sun ; and 

 the results of this kind, which he has already obta!ined, confirm 

 the conjectures of Bode, Schroeter, Herschell, §'c. — Proceedings 

 of the Royal Academy at Paris, — Ann. de Chim. xxvii. 89. 



6. Temperature of the Sun, &c. — M. Dulong communicated a 

 letter from M. Pouillet, in which that philosopher announced, that 

 he was occupied with experiments relative to the measure of very 

 elevated temperatures, such as those on the surface of incan- 

 descent bodies, or bodies in ignition, of flames, and particularly of 

 the sun. The instrument used by M. Pouillet to obtain these 

 results is founded on the properties of radiant heat, and princi- 

 pally on this datum ; that a body, the bulb of a thermometer for 

 instance, perfectly insulated in the midst of a sphere of ice, but so . 

 placed as to receive the rays of the sun through a circular aperture 

 of such a form and position, that ail the lines forming tangents to 

 the sun and the ball may pass through it, will be heated precisely 

 in the same manner as if it were supposed that a portion of the 

 surface of the sun, or of a body heated to the same temperature 

 exactly filled the aperture in the ice. M. Pouillet, among other 

 results, states, that the temperature of the sun thus determined is 

 1400 degrees (2552° F.) — Proceedings of the Society of Pharmacy 

 of Paris. — Jour, de Pharm. 1824, 415. 



7. Security of Steam Engines. — The Royal Academy of Paris, has 

 been called upon by the government, to report on the means proper 

 to be adopted for the prevention of accidents and injury from the 

 explosion of steam-engine boilers. The means proposed had the 

 double object of preventing the rupture of the boilers, or in case of 

 their destruction, preventing injury to neighbouring buildings. 

 They directed that the boiler should be proved by the hydraulic 

 press, with a force five times that which they would have to bear 

 during the working of the engines: that a safety valve should be 

 attached to the boiler and locked up, the valve being so loaded as 

 to open at a pressure just above that by which the boilers have been 

 tried: that the boiler should be surrounded by a wall of masonry one 

 metre (39.371 inches) in thickness; aninterval of ametre being left 

 between the boiler and the wall, and again between the wall and the 

 neighbouring buildings. Another precaution has been added by 

 M. Dupin, and adopted by the Academy ; namely, the introduction 

 of a metallic plug into the upper surface of the boilers, formed of 

 such an alloy as should melt at a temperature a few degrees above 

 that at which the engine is intended to work. 



In consequence of this application, it became necessary to form 

 a table of the pressure and temperature of vapour. The academy 

 appear very doubtful of estimations as yet published, but give the 



