the specific heats of certain solids. 279 



water at the instant the metal is immersed, and keeping it out till 

 near the conclusion of the experiment, we not only have a better 

 opportunity to agitate the liquid, but also avoid the deception just 

 referred to. 



If the experiment be commenced precisely at the evaporating 

 point, the bulb of the thermometer covered with a film of water will 

 be retained at that point and no correction required. 



The formula for the fourth method of determining specific heat, 

 which may serve as a verification of the one just presented, is found- 

 ed on the fact that the weight of vapor generated by a given weight 

 of metal is proportionate to the weight, temperature, and specific 

 heat of the metal employed. The experiments in this case all ter- 

 minate at the boiling point, but may commence at any known supe- 

 rior temperatiu-e. The result obtained will therefore be the mean 

 specific heat between the temperature of boiling water, and that at 

 which the metal enters the liquid. Calling 



i = the w^eight of metal employed, 



t =its temperature above boiling point at immersion, and 



2= its mean specific heat, fi-om boiling point to the temperature 

 at which it is immersed ; also, 



«=the weight of vapor produced by the action of i, and 



/ = the latent heat of vapor from water boiling in the open air at 

 the time and place of the experiment. 



Then, by the above statement, we have (supposing no heat lost 



by any other means than vaporization) the effect =vl, and the cause 



=it. The latter is on the supposition that the experiment ceases, 



and the loss of weight in w'ater is ascertained, the moment the metal 



vl 

 has come down to the boihng point. Hence itz=vl, and z=—' (9.) 



Also, as above stated, the temperature t can be found when z is 



vl 

 known; thus, ^=^ — (lO-) 



Collecting the foregoing formulas into a single view, we have the 

 following table. 



