SECT. 1.] 



THE STEAM ENGINE. 



15 



FIG. 6. 



piston descends, the wheels a, b, c, move forward, and the ropes g, h, cause the 

 wheels e, d, to move, the wheel e forward, and the wheel d backward, and the 

 latter raises the weight G, which moves the wheel d forward during the ascent of 

 the piston ; consequently, the axis A B, with the paddle wheels, would be constantly 

 moved round in the same direction and by an equable force. This is certainly 

 a beautiful contrivance for rendering so irregular a first mover equable ; and, con- 

 sidering the object it was intended for, it is not a complex arrangement ; for 

 besides equalizing the power, it gives a means of increasing or diminishing the 

 velocity in the ratios of the diameters of the wheels. The pamphlet of Hulls bears 

 evidence of being the work of an ingenious and well-informed mind ; and we must 

 regret the causes which prevented his views meeting the encouragement they 

 merited. ' 



1739. BERNARD BELIDOR; born 1698, died 1761. 



15. Belidor, so eminently distinguished as a writer on the theory and practice 

 both of civil and military engineering, treated of the steam engine in 1739, and 

 undoubtedly presented the most accurate information then existing in France on 

 the subject. " He gives a slight sketch of its history ; and infers, from his in- 

 quiries, that the three nations of Europe most advanced in the pursuit of know- 



1 Hulls's pamphlet may be seen at the British Museum or the London Institution ; and many 

 civil engineers have succeeded in adding it to their own collections. 



2 Architecture Hydraulique, torn. ii. p. 300 331. 



