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LXX. Onanew Method of applying the Power of Man to the 
moving of Machinery, with at least sia times the Effect that 
can be produced by mere muscular Exertion. By the Rev. 
Dr. EpMuND CaRtwricur. 
To Mr. Tilloch. 
Dear Sir, (Hivine lately discovered a method by which a 
man’s power in giving motion to machinery of any kind, may be 
employed with at least six times the effect that may be obtained by 
mere muscular force, I am desirous of giving a discovery, embrac- 
ing such a variety of purposes, the most extensive publicity :— 
and this I cannot do more effectually than through the medium 
of your Philosophical Magazine. The power with which a man 
can work through the day, and every day, is commonly calculated 
at 28 or 30 |bs. If, therefore, a way can be pointed out by which 
the whole of his absolute gravity can be brought into constant 
action, he will increase his power (calculating upon the average) 
as six to one. Now this is to be done by means so simple and 
obvious, that it seems nothing less than a miracle that the idea 
did not occur, even to the common knife-grinder, centuries ago. 
It is nothing more than having two cranks upon the axis to be 
moved, standing perpendicularly to each other, and the operator 
shifting his weight alternately from the treddle of one crank to 
the other. If the diameter of the crank’s revolution does not 
exceed seven or eight inches, the muscular exertion will be tri- 
fling. To bring the whole or such part of the operator’s mus- 
cular force into action as may occasionally be wanted, he might 
have straps upon his shoulders, such as are used by chair-men, 
which, being fixed to any convenient part of the machine, would 
enable him to add to his weight double the power of his abso- 
lute gravity ; and this additional weight, when not wanted, he 
could be relieved from by a very slight inclination of tHe shoul- 
ders. ‘These ideas I have actually reduced to practice, and have 
had a four-wheeled carriage made, which has fully ascertained 
the principles that are here laid down. To this carriage I at- 
tached a plough. We had not, however, proceeded above twenty 
yards, when being impatient to try the full power of the machine, 
1 ordered the men to add their muscular force to that of their 
gravity; when the machinery which I had substituted in the place 
of treddles gave way, and terminated the business for that day. 
On my return home I shall expect to find the damage repaired. 
My substitutes for cranks are ratchet-wheels acted upon by tred- 
dles which have pauls upon them, which, when the treddles are 
lifted up, fall into a ratchet. The treddles are lifted up by 
means of a strap on the treddle under which the operator passes 
his foot. As 
