16 president's address, 



1st. "I use the vessels in which the steam is to act, and 

 which in other steam engines are called cylinders." 



2nd. ''I employ the steam, after it has acted in the first 

 vessel, to operate a second time in the other, by 

 permitting it to expand itself, which I do by 

 connecting the vessels together and forming proper 

 channels and apertures whereby the steam shall 

 occasionally go in and out of the said vessels." 



3rd. " I condense the steam by causing it to pass in contact 

 with metallic surfaces, while water is applied to 

 the opposite side." 



4th. " To discharge the engine of the water used to 

 condense the steam, I suspend a column of water 

 in a tube or vessel constructed for that purpose, 

 on the principles of the barometer, the upper end 

 having open communication with the steam vessels 

 and the lower end immersed into a vessel of water.'? 



5th. " To discharge the air which enters the steam vessels 

 with the condensing water or otherwise, I introduce 

 it into a separate vessel, whence it is protruded by 

 the admission of steam." 



6th. "That the condensed vapour shall not remain in the 

 steam vessels in which the steam is condensed, I 

 collect it into another vessel, which has open 

 communication with the steam vessel, and the 

 water in the mine or river." 



Lastly. " In cases where the atmosphere is to be employed 



to act on the piston, I use a piston so constructed 



as to admit steam round its periphery, and in 



contact with the sides of the steam vessel, thereby 



to prevent the external air from passing in between 



the piston and the sides of the steam vessel." 



In an enclyclopeedia published at Edinburgh, Hornblower 



describes his first model of a double acting engine as having 



been made in 1776, and which worked well, but was not carried 



any further in deference to his father's advice, relative to 



mechanical difficulties in his use of a lid to the steam vessels. 



