536 Intelligence and Miscellaneous Articles. 



6. With simple or composite gases, the specific heat at a constant 

 volume is represented by the number of simple atoms of which they 

 are composed, or by a simple fraction of this number. 



7. For each simple or compound body there exists a ponderable 

 molecule, the mass of which is always in simple proportion to the 

 chemical equivalent, and which possesses the power of producing 

 the same mechanical work when it is solicited by the same force or 

 by the same quantity of heat. We shall give it the name of mecha- 

 nical equivalent. Tlie mass of this molecule will be that which must 

 be taken as unity in problems of chemical dynamics. 



Velocities of sound at the 



Names of substances. temperature of 0° C. 



Air 33300 metres. 



Sulphurous acid 209'00 . . 



Sulphuretted hydrogen 289-27 . . 



Deutoxide of nitrogen 325"00 



Carbonic acid 256-83 . . 



Protoxide of nitrogen . . 256-45 



Ammonia 415-00 . . 



Cyanogen 229-48 , . 



Muriatic acid 297-00 .. 



Protocarbonated hydrogen .... 431-82 



Oxide of carbon 339-76 . . 



Bicarbonated hydrogen 318-73 



Fluoride of silicium 167-40 



Aqueous vapour 401 '00 . . 



Vapour of sulphuret of carbon . . 189-00 



Vapour of alcohol 230-59 . . 



Vapour of ffither 179-20 .. 



Vapour of muriatic sether 199-00 



-—Comptes Rendus, March 2, 1857, p. 464. 



THE IMPROVED INDUCTION COIL. 



To the Editors of the Philosophical Magazine and Journal, 



Gentlemen, 

 I should not have replied to the Note from Mr. Bentley, contained 

 in your last Number, but that I wish to prevent any misinterpretation 

 of my remarks relative to Dr. Noad and himself. Mr. Bentley, in 

 coming forward to vindicate the disititerested conduct of Dr. Noad, 

 has quoted detached portions of my statements in such a connexion 

 with each other as to endeavour to make it appear that I have com- 

 plained of commercial injury sustained by Dr. Noad's having ex- 

 hibited his machine, and asks, " Would it have been just to suppress 

 my humble attempts at improvement for the sake of Mr. Hearder's 

 pecuniary advantage }" Now I beg to say that this is quite a 

 mistake. I have not complained of Dr. Noad's having introduced 

 Mr. Bentley's machine to the public, because it was part of his 

 business, as a public lecturer, to herald scientific improvements. I 

 have only complained that Dr. Noad should have suppressed my 

 inventions on that occasion, knowing that they had been made 



