ON SUrERHEATED STEAM. 



183 



still occasion the waste of more thousands yearly 

 than it would cost pounds to set it at rest for ever, 

 by a series of the most elaborate experiments, 

 conducted on the most expensive scale. To this 

 end, however, a new thermometric scale, graduated 

 to equal additions of heat, and not of expansion, 

 seems one indispensable requisite, even before all 

 else ; and more exact determinations of the specific 

 heats of steam and air, compared to water, are 

 loudly called for, the discrepancies between the 

 numbers obtained for these by Crawford, De la 

 Roche, and Berard, the authorities commonly 

 followed, being such as to destroy all confidence 

 in calculations founded on either." 



To enter, therefore, first, upon the considera- 

 tion of steam-boilers of high-pressure-saturated 

 Steam, we will now refer to the diagram of one, 

 Fig. 20, in which the relative positions of the water 



Fig. 20. 



and steam will be obvious to all : the steam, as it 

 is generated, is carried away from thence to its 

 uses. Now I do not intend to touch upon the 

 questions of latent heat, consumption of fuel,, 

 horse-power, shapes of boilers, &c. : those wha 



