60 Mr Russell on the Fallacies of the 



it from every other means of producing that conversion, and 

 which appear to be so perfectly adapted to the nature of steam 

 and the constitution of solid matter, that we are indebted to it 

 materially, although indirectly, for the very great advantages 

 .we derive from the modern steam-engine as a source of mecha- 

 nical power. Ingenuity has been taxed to the utmost to find 

 substitutes for it, which should remedy the (imaginary) defects 

 of the crank, but the mighty element has disdained them all, 

 pounded them to powder, and thrown them from her. Like 

 unskilful keepers, they have attempted to control a power by 

 means which have only encountered the force they were de- 

 signed to direct ; and, after many vain efforts, it is found that 

 the crank is the magic rod under which alone the mighty force 

 of the element becomes peaceful and docile. Wheels, sectors, 

 and racks, in various combinations, have been made to assume 

 the functions of the crank, but they have uniformly been de- 

 clared incapable. Once or twice it has happened that a substi- 

 tute was obtained, but it was soon found that these (the sun 

 and planet motion, for example) were only the crank in dis- 

 guise ; and the useless mask was speedily dispensed with when 

 the cause of its assumption had ceased to exist. It was an in- 

 vidious patent alone that induced the immortal Watt to give 

 the name of Sun and Planet to two wheels, placed one at the 

 base and another at the apex of the crank. The disguise dis- 

 appeared as the patent expired, and the simple unencumbered 

 crank resumed its well-merited station. 



The peculiarities of the crank which give it its unapproach- 

 able perfection as an elementary machine, I shall now go on to 

 describe. 



1st, I would observe, that in the reciprocating piston in a 

 steam-engine the following things occur : — The piston is to be 

 put in motion in one direction, then stopped ; then put in mo- 

 tion in the opposite direction, stopped again ; motion in the ori- 

 ginal direction begcun and once more made to cease. At the com- 

 mencement of the motion downward, a valve is to be opened for 

 the entrance of the steam above the piston, which valve must be 

 closed at the end of the stroke, and at the same instant in which 

 one steam-valve closes, an opposite one must be opened to ad- 

 mit steam below the piston; at the same instant, also, a valve 

 of eduction for the first portion of the steam must be opened. 



