H Dr. Fordyce’s Ledlure 
continue in motion, in the fame direction, if it did not meet 
with another, on which it impinged ; and after the impinging, 
there would be the fame quantity of motion and red: in both 
bodies taken together, as was before. If we confider equal 
motion, in direct contrary direction, as reft; motion, or red:, 
produced in a body by the above means, I lhall call commu- 
nicated. 
If two fimple particles of matter, of any fpecies, not far- 
ther diftant from one another than the fun is from the earth, 
were both at perfect red, thefe two particles would indantly 
begin to move toward one another, if no other particle of 
matter whatever exided. 
I do not mean to tire my learned Audience with demondra- 
tion of proportions fo well known. 
There would, therefore, be an impulfe, producing motion 
between thefe bodies, without any contact. 
Motions produced in this way, I call original motions. 
The fird confideration with regard to any particular motion , 
is, therefore, whether it be an original or communicated mo- 
tion. If it be an original motion, it will follow the laws of 
that particular fpecies of original motion ; if it be a communi- 
cated motion, it will follow the laws of communicated motion. 
Many obfervations fhew, that mufcular motion is not a 
communicated motion, and therefore an original one. 
In any fydem of bodies, or particles of matter, affecting 
one another only by the motions already exiding in them 
being communicated to one another, they may diminifh their 
motion, or bring one another to red ; but they never can in- 
creafe the motion exiding in the whole. It happens frequently, 
that the motions in the animal body are increaled, without any 
alteration of external applications to it ; the caies are fo nume- 
rous, that it is hardly worth bringing an example : we might 
mention 
