in the Construction of Steam-Eng'mes. 337 



densalion of it and waste of'hcat; for the real expansive 

 force of steam, I am inclined to believe, from the experi- 

 ments I have made, increases in a regular ratio a little be- 

 yond what I have stated, though I would not recommend 

 that it should be calculated higher in applying it to steam- 

 engines, because the difficulty of confining and managing. 

 it increases also as the elasticity of the steam is increased, 

 or as its temperature is increased. 



And here it may be of use to the public to state some 

 facts respecting different degrees of temperature required to 

 bring steam to, and maintain it at, different expansive forces 

 above the weight of the atmosphere ; because the tempera- 

 ture of the steam indicated by a thermometer, having its 

 bulb in the boiler which produces it, will indicate the ex- 

 pansive force of the steam, without the trouble and incon- 

 venience of changing the weights on the valve, by which 

 its force is regulated for the work intended to be performed 

 by it, and \\'hich valve acts as a connnon safety-valve, so 

 that those who attend the boiler will know with sufficient 

 precision, by looking at the thermometer, how they ought 

 to feed the fire; and, moreover, the relation between the 

 temperature and the expansive force being known, the dan- 

 ger of accidents from the safety-valve bcconiing deranged 

 will be lessened, for the workman will naturally be led to 

 notice whether the safety-valve acts freely when the ther- 

 mometer has risen to the degree that answers to the weight 

 with which the valve is loaded for working. T have found 

 by actual experiment, setting out from the boiling point, 

 or two hundred and twelve deo;rees of the thermometer, 

 comn:only employed in this country, which is that of Fah- 

 renheit, at which degree steam of water is only equal to the 

 pressure of the atmosphere, that, in order to give it an in- 

 c'cased elastic force equal to five pounds the square inch, 

 the temperature must be raised fifteen or sixteen degrees, 

 or to about two hundred and twenty-seven and a hall, when 

 the steam will have acquired a power to expand itself to five 

 times its volume, and still be equal to the atmosphere, and 

 capable of being applied as such in the working of steam- 

 engines according to my said invention. And with regard 

 to various other pressures, temperatures, and expansive 

 forces of steam, the same are shown in the following table: 



Vol. 21. No. 92, Jan. 1806. Y Talle 



