Steam-Engine—Physics. 137 
PHYSICS, MECHANICS, AND CHEMISTRY. 
a BEG cce- 
Ant. XV. On the Revolving Steam-Engine, recently invented 
by Samust Money, and Patented to him on the 14th July, 
1815. 
To Professor Silliman. 
‘Sir, 
Tie successful employment of the steam-engine, in navi- 
gating the rivers and inland waters of the United States, and 
the probable extension of this mode of conveyance of persons 
and’ property, makes those improvements desirable which 
adapt the steam-engine to this purpose with less complication 
and expense, placing it more within reach of individual enter- 
prise, and rendering it even useful on our small rivers and 
canals, 
The steam-engine, though often seen in operation, is not 
readily understood by an observer, without an acquaintance 
with the facts in natural philosophy on which its power de- 
pends: and it may elucidate the subject of this communication 
to advert, for a moment, to the gradations by which this im- 
portant machine has attained its present perfection. 
It will be recollected that as early as 1663, the Marquis of 
Worcester published some obscure hints of a mechanical power 
derived from the elastic force of steam. 
In 1669, Savary, availing himself of the suggestion, and pur- 
pore the subject more scientifically, invented his engine, con- 
sisting of an apparatus to cause a vacuum by the condensation 
of steam, so that the water to be raised would thereupon, by 
the external weight of the atmosphere, rise into the chamber 
of the apparatus, which the steam had occupied. 
As caloric becomes latent in the steam which it forms at 212° 
of Fahrenheit, and the steam thus form pies 1800 times th 
hulk of the water composing it; and as it returns instantly to 
ALCS Cit 
