Relation of the Laws of Mechanics to Perpetual Motion. 177 
cording to the means which are used to effect the object, ot ac- 
cording to the characters of the different projectors. The 
of science will be liable to embarrassments of one kind; the on 
mechanician, to those of another. The chief impediments i in the ° 
way of the man of science are certain general principles, denom- 
inated laws of nature. His ingenuity is exercised in er ae 
° 
the same pe from which he started. 4 
Nothing but what is capable of pee motion, can be the 4 
cause of perpetual motion. The moving forces which are com- 
parts of the machine. They are forces applied from without. , 
But steam, springs, and weights may belong to the machine itself. 
Of these, the weight of a heavy body is that which is generally ; 
made use of, to produce perpetual motion. - A weight is a very ~~. 
by descending ; and that when it reaches the ground, its ope-*~ 
ration ceases. If it could be made to descend’ and then as- > iy! 
cend, Rey the same force, it migut teed a machine i in perpetual “s 
actio *’ 
The difficulty is not, as some seem sto. have: viet tha see fy ; 
weight can move a bo ody in one direction only. It can 
Motion in any direction ; not indeed by mere pressure, but } 
aid of some very simple apparatus, for instance, a cgrd passin 
over a pulley. Nothing is easier than to change the’ rection in fo. 
wick a given pioet is to act pe me the object to be moyéd. A. 
weight mé ~make a body either ascend, or descend, or. Moye “: 
” * horizontally.” “But the real diffieclvy is, ‘that the , power. will nets 
ere. at 8 ei epit AN reached the: ground. “Its oper 0 re then” 
i ook ahge UE 
: 
e” 
ie 
great thing wante 
ee m vetnent aia 
ance depend unless 
force, There i is One in 
ECOND Srnizs, vel. x, ‘No: 
Pl 
St a. 
