398 TRANSACTIONS OF THE 



cauldron or vessel for boiling water, we have no authentic record. It has 

 been suggested, however, that he may have used a modification of the en- 

 gine of Hero, the elder, who lived 130 years before the Christian era ; and 

 in his works he shows beyond doubt a recognition of the two properties of 

 steam ; expansion, and contraction, applied nearly 2,000 years before being 

 made available for any practical purposes. 



The engine of the Marquis of Worcester, although claimed by him to 

 draw or haul boats up rivers against the stream, is entitled to little atten- 

 tion. 



Papins' project next follows. Although he is entitled to the invention 

 of the safety valve for boilers, and for a machine containing some of the 

 rudiments of a condensing engine, he wholly failed to put his project of 

 navigation to a practical test. He employed two or three steam cylinders ; 

 a rack was placed on the piston rod, working into a pinion fastened on the 

 axle of the revolving paddles. When one piston was ascending, the others 

 were working downwards, and as they would give contrary motions, one 

 was detached while the other was in action, and by these means the motion 

 was made continuous and regular. 



In 1731, Dr. John Allen proposed a plan for propelling vessels, by 

 forcing a stream of water or air out of a tunnel or pipe at the stern of a 

 vessel, which was to be urged forward by its reaction, imitating says Dr. 

 Allen, what the Author of nature has shown us in the swimming of fishes, 

 who proceed in their progressive motion not by the vibration of their fins 

 as oars, but by protusion with their tails ; and water fowls swim forward 

 by paddling their feet beyond their bodies. This plan, although modified 

 from time to time, has not proved by experiment to posses any advantage. 



Jonathan Hull, in 1737, published a description and draught of a new 

 machine to carry ships out of harbor against wind and tide. This plan 

 does not seem to have been put in practice, nor does he seem to have added 

 anything new to the known method of propulsion, except the crank motion, 

 of which he was the inventor and patentee. Hull proposed placing an at- 

 mospheric engine in a tug boat, and to communicate its power by means of 

 ropes to the axis of a kind of paddle wheel, mounted in a frame-work pro- 

 jecting from the stern of the vessel. A contrivance was added for contin- 

 uing the motion of the paddles, by the descent of counter-balancing weights 

 in the intervals of the stroke of the piston. 



To guard against the injury of the fans, or paddles, by the violence of 

 the waves, Hull proposed to lay pieces of timber so as to swim on each side 

 of them. 



He also suggested that in inland rivers, where the bottom could possibly 

 be reached, the fans or paddles might be taken out, and cranks placed on 

 the hinder axis, on which the paddles were usually fixed, to strike a shaft 

 to the bottom of the river and drive the vessel forward. 



The difiiculty in counter balancing the ascending stroke of the single 

 action engine, proved an insurmountable objection to Hull's plan, and, as 

 has been observed, a ship containing such a propelling machine would be 



