46 PROCEEDINGS OF THE 



A commnnication from the Astronomer Royal, ' On Boiler Explosions',' was read 

 by Mr. P. Le Neve Foster. Ti>e author stated that, iu considering the cause of 

 the extensive mischief done by the bursting of a high-pressure boiler, it is evident 

 that the small quantity of steam contained in the steam chamber has very little to 

 do with it. That steam may immediately produce the rupture, but as soon as the 

 rupture is made, and some steam escapes, and the pressure on the water is dimin- 

 ished a portion of the water is immediately converted into steam at a slightly 

 lower temperature and lower pressure, and this, in- the same way, is followed by 

 other steam at still lower temperature and pressure, and so on till the temperature 

 is reduced to 212° Fahr. and the pressure to 0. Then there remains in the boiler 

 a portion of water at the boiling point, the other portion having gone ofif in the 

 shape of steam of continually diminishing pressure. Prom this it is evident that the 

 destructive energy of the steam, when a certain pressure is shown by the steam 

 gauge, is proportional to the quantity of water in the boiler. By the assistance of 

 Prof. Miller, of Cambridge, Messrs. Ransome, of Ipswich, and George Biddell, Esq., 

 the author has been able to obtain a result which he believes to be worthy of con- 

 fidence. He fir&t stated, as the immediate result of Mr. Biddell's experiments, 

 that when there were in the boiler of a small locomotive 22 cubic feet of water, 

 at the pressure of 60 lb. per square inch, and the fire was raked out, and the 

 steam was allowed gently to escape, with perfect security against priming, the 

 quantity of water which passed off before the pressure was reduced to was 2|- 

 cubic feet or ^ of the whole. In regard to the use made of Prof. Miller's theory, 

 Prof Miller had succeeded in obtaining a numerical expression for the pressure of 

 steam at twelve different measures of the volume occupied by water and steam, 

 which expression the author has succeeded in integrating accurately, and had thus 

 obtained an accurate numerical expression for the destructive energy of steam. In 

 regard to the use of General Didion's experiments, these experiments gave the 

 velocity of the ball, in cannon of different sizes, produced by different charges of 



powder. The author found, by trial with the formula g^ x weight of powder, 

 •which of these experiments exhibits the greatest energy per kilogramme of pow- 

 der, and had adopted it in the comparison. The result is as follows : — the destruc- 

 tive energy of one cubic foot of water, at 60 lb. pressure per square inch is equal 

 to the destructive energy of two English pounds of gunpowder in General Didion's 

 cannon experiments ; Gen. Didion's experiments were made as the author understood 

 with smooth bored cannon. It cannot be doubted that much energy is lost in the win- 

 dage ; some also from the circumstance that the propelling power ceases at the muz- 

 zle of the gun, before all the energy is expended ; and some from the coolness of the 

 metal. If we suppose that from all cau^s one-half of the energy is lost, then we have 

 this simple result: the gauge-pressure being 60 lb. per square inch, 1 cubic foot of 

 water is as destructive as 1 lb. of gunpowder. In one of Mr. Biddell's experi- 

 ments, the steam-valve was opened rather suddenly, and the steam escaped in- 

 stantly with a report like that of a very heavy piece of ordnance. This is not to 

 be wondered at ; it appears from the comparison above that the efifect was the 

 same as that of firing a cannon whose charge is 44 lb. of powder. 



« On Spectral Analysis,' by Prof. Plucker.— It is generally admitted now, that 

 every gaseous body rendered luminous by heat or electricity sends out a peculiar 



