11 
The force of gravitation has its practical application in the 
ordinary forms of water-wheels, the falling water producing a 
continuous circular motion. In the hydraulic pressure engine, 
of which we have a beautiful model in the museum, the gravi- 
tating power of the water is the moving force. In the wind- 
mill we see the operation of the same power ; and in the earlier 
engines, as those of Newcomen, Savery, and Watt’s first single 
acting engine, the return of a heavy mass under the influence 
of gravitation and the atmospheric pressure — a result of the 
same principle — was the leading element of power. The works 
of Archimides and of Ilero of Alexandria show us that the 
ancients were well acquainted with the operations of this 
agent, although they had not arrived at any correct idea of its 
law 7 of action. It is to a neglect of the laws of gravitating 
force, and of the principle of action and reaction which prevails 
in every mode of motion, that the idle problem of producing 
perpetual motion has so frequently led ingenious minds aside 
from the path of usefulness which they would otherwise in all 
probability have pursued. 
To continue our examination of the importance of minute 
observation, every step of progress from the employment of 
steam to produce a continuous motion, by Ptolomy Philadelphus, 
130 years B. C., to the discovery by Watt of the expansive force 
of steam in 1782, might be quoted in exemplification. 
We find Branca and Kircher employing the force of a jet of 
steam to drive the vanes of a wheel. 
Baptista Porta observed the pressure exerted by confined 
steam, and he used it to raise water. 
The discovery of the pressure of the air, and the investigations 
of Torricelli, Pascal, Guericke, and Boyle, led to the construction 
of engines by Worcester and Papin, in which the elastic force 
of steam and atmospheric pressure were combined in action. 
Thomas Savery, carefully studying all that had been done 
previously, appears to have first conceived the correct idea of the 
force, and to have applied it with much greater success than any 
of his predecessors. In 1698 he got a patent for his discovery, 
calling it an invention “ for raising water, and occasioning motion 
to all sorts of millwoi'Jc, by the impellent force of fire." 
