x, le] Z | 
316 * On the Rapid Production of Steam. 
water by mucture, involves the necessity of considering the increase 
of. temperature, i in the containing vessel, together with its separate 
heat, before any accurate result can be anticipated. The 
od of generating steam from an apparatus kept at a uniform 
temperature, and by means of bodies of known superior temperatures, 
! is, I conceive, less liable to objection from any of these sources of 
fallacy. ‘The only modifying cause, which deserves much attention, 
is the barometric pressure during the experiment, which involves also 
_.a consideration of the specific heat of steam under different ‘press- 
_ ures, but as this source of error may be obviated by performing ex- 
periments at uniform pressures, we need hardly take it into view, in 
estimating the general correctness of the mode now Laon of 
verifying the specific heats of bodies. 
By knowing at what temperature we plunge a piece of e 
der boiling water, the weight of the metal, and its mean capacity for 
heat, we may readily infer, from what is known of the quantity of la- 
tent heat in the unit by weight of steam, what weight of the Tiquid 
will be boiled off while the metal is reduced from a psa tem- 
perature down to 212°, 
Thus let the ca eat of the metal above 212° =¢ 
Its weight “ah ave «tie | 
Its mean capacity between 212° and the known temperature =e 
The latent heator™ atmospheric’ steam. =/ 
The ue of steam which the metal can produce =s 
Then will = Thus, suppose ¢=2000°,.c=.1111, w= 1602. 
tew 2000%.1111 X16 2 
and 1-=990, then we shall have T= 00 a: 
ounces. 
‘From the above formula we derive immediately an ixpnceie for 
the tae when all the other elements are known 5 for iris 
whence t=—5 so o that when we would determine the actual tem- 
perature of a body above 212°, whose specific caloric has been care- 
fully ascertained, we have only to find what weight of vapor it 
produce in coming down to the point of e ebullitéon ; multiply this by 
the latent heat in steam, and divide the product by the product of the 
weight of heated matter multiplied by its specific heat. Upon the 
basis of this proposition I have constructed an instrument called the 
steam ee, to be applied to the measurement of heat in incal- 
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