of the Destructive Energy in Steam-boiler Explosions. 331 



department of physics I have often been indebted), to enable me 

 to give numerical values to the expressions involved. At that 

 epoch, however, the theories and experiments on steam were not 

 sufficiently advanced, and I was compelled to lay aside the 

 inquiry for a time. 



6. In the spring of the present year I requested Messrs. 

 Ransomes and Sims, of Ipswich, to furnish me with an experi- 

 mental result on the quantity of water escaping from a high- 

 pressure boiler in the form of steam when the valve is gradually 

 opened. This experiment was undertaken by George A. Biddell, 

 Esq., Engineering Superintendent of the Orwell Works. The 

 result was that, when the bulk 22 cubic feet of water in a loco- 

 motive boiler was raised to the temperature which produced a 

 pressure of 60 lbs. per square inch, and when after raking out 

 the fire the valve was gradually opened with every precaution 

 against priming, the quantity of water which escaped in the 

 form of steam was 2 j cubic feet, or one-eighth of the whole. 



7. Possessed of this experimental fact, I again referred to 

 Professor Miller for such theories and citations of experiments 

 as might be required. And by his kind assistance I was enabled 

 to complete the investigation. And here I may state that the 

 whole which follows is Professor Miller's, with the exception of 

 the integration of the steam-pressures, the inference from the 

 cannon-experiments, and the comparison of steam and gun- 

 powder. 



8. In giving the heads of Professor Miller's theory, I must 

 premise that the temperatures are Centigrade, the unit of linear 

 measure is the metre, and the unit of weight is the kilogramme. 

 The formula adopted as connecting the volume of steam with 

 the volume of water (at maximum density) from which it was 

 generated, is Fairbairn's and Tate's (Phil. Trans. 1860, p. 219). 

 The formula for the number of calories required to convert 

 water into saturated steam of temperature T, and the pressure of 

 saturated steam at temperature T, are from Regnault (Memoires 

 de VInstitut, vol. xxi. pp. 748 and 728). 



9. The first part of Professor Miller's investigation applies to 

 Mr. Biddell's experiment. The steam-pressure of 60 lbs. per 

 square inch is represented by a column of mercury (at 0°) 

 3*1028 metres in height. Adding the atmospheric pressure 

 0*76 metre, the entire elastic force of the steam is represented 

 by a column of mercury 3*8628 metres in height. The corre- 

 sponding temperature of saturated steam, by Regnault' s Table, 

 is 152°*84. Now the quantity of water is 22 cubic feet, which 

 at 100° weigh 597*1 kilogs., and the heat requisite to raise the 

 temperature of this water from 0° to 152°*84 is 597*1 x 154*38 

 calories (the last number being derived from Regnault' s formula 



Z2 



