62 ANNUAL OF SCIENTIFIC DISCOVERY. 



entirely now aspect. So far from the metal in large guns diminishing in 

 strength in the proportion assumed, it will be a matter for inquiry how it 

 resists the great strain to which it is subjected, rather than why it yields; 

 for we find, from the experiments described above, that a sixty-eight 

 pounder gun, which has a calibre of twice the diameter of a nine-pounder 

 gun, must, when fired with the same proportionate charge of powder as the 

 latter, continually be subject to as great a strain as the latter would suffer if 

 always fired with the proof-charge, which is three times the quantity of the 

 ordinary service-charge. Proc. Royal Soc. 



THE DENSITY AND TEMPERATURE OF STEAM. 



We extract from the London Engineer the following account read before 

 the British Association for the Advancement of Science, by William Fairbaim, 

 F. R. S. of some researches to determine the density of steam at all tem- 

 peratures : 



I propose to give a short sketch of an apparatus and the results of the 

 earlier experiments which, in conjunction with my friend Mr. Thomas Tate, 

 I have been investigating by direct experiments, with the intention of deter- 

 mining the law of the density of steam and other condensable vapors ; and 

 thus to solve a hitherto almost untouched problem by an experimental 

 method, which will verify or correct the theoretical speculations in regard to 

 the relation between the specific A'olumc and temperature of steam and other 

 vapors. The experiments are being conducted, it is believed, upon an en- 

 tirely novel and original principle, and one which is applicable at any tem- 

 perature and pressure capable of being sustained by glass vessels. 



For a perfect gas, the law which regulates the relation between temperature 

 and volume is known as Gay-Lussac's or Dalton's law, and is expressed by 

 the equation 



V X P 458 + tl 



(1.) 



V\ X PI " " 458 + t 



Now, density of steam has been determined with accuracy by direct experi- 

 ment at the temperature of two hundred and twelve degrees and at that 

 temperature only by the method of Dumas. At two hundred and twelve 

 degrees Fahrenheit its density is such that its volume is one thousand six 

 hundred and seventy times that of the water that produced it. Substituting 

 these values of volume, temperature, and pressure, we get for the volume of 

 steam from a unit of water at any other temperature, 



(2.) V 





This is the well-known and received formula from which all the tables of 

 the density of steam have hitherto been deduced, and on which calculations 

 on the duty of steam-engines have been founded. Up to the present time, 

 however, this formula has never been verified by direct experiment, nor arc 

 the methods hitherto employed in determining the density of gases and 

 vapors applicable in this case, except at the boiling temperature of the liquid 

 at the ordinary atmospheric pressure. But, on the other hand, theoretical 



