432 



SCIENCE. 



[N. S. Vol. III. No. 64. 



stituted of particles ; that the motion of the 

 particles within the body should remain 

 within the sphere of the body, their paths 

 must be composite. In order that their 

 paths may be composite there must be a suf- 

 ficient number of collisions to deflect these 

 several particles and retain them within that 

 sphere. 



If the body itself is moved the paths of 

 the several particles in the average must 

 thus be rendered less composite, that is, the 

 number of collisions must be diminished. 

 The motion of the body as such, therefore, 

 is accomplished by diminishing the deflec- 

 tions within the body and straightening 

 their paths. The translatory motion of a 

 body is a straightening of the paths of the 

 particles of which the body is composed. 



Imagine a man walking in a circle of ten 

 feet radius. The sphere of his motion is 

 within the circumference. He may soon 

 walk a mile and never be more than twenty 

 feet away from any given point in the cir- 

 cumference ; change his direction so that his 

 path is straightened, and he may soon be a 

 mile away. A body of men walking in a 

 circle remain together as a body within the 

 circumference of the circle as it moves with 

 the earth ; change their paths to a cj'cloid 

 and the body of men will move away or 

 change their paths to parallel right lines, 

 and as a body they may soon be a mile 

 away and still in a circle. In the same man- 

 ner the molecules of the wooden ball are in 

 motion within the theater of the ball, so that 

 they do not pass beyond its boundaries, yet 

 impose upon each molecule a change of di- 

 rection in such manner that they all move 

 a little more in one course and a translation 

 of the ball is affected by a change of direc- 

 tion in the motion of its constituent mole- 

 cules, and the ball still remains as an incor- 

 porated body. It is thus possible to explain 

 molar motion of the ball as a change in di- 

 rection of the motion of its molecular parts, 

 without assuming an increase of speed in 



the parts. By such an assumption the molar 

 motion perceived by vision would be legiti- 

 mately derived from the molecular motion 

 known by reason, and appear as a change 

 of direction in the telluric motion of the ball. 



No motion would be created or destroyed, 

 and action and reaction would remain 

 equal, while the apparent molar motion 

 would be explained by a change of direction 

 in molecular motions, very minute as com- 

 pared with the composite paths of the sev- 

 eral molecules and the composite path of 

 the body in its telluric motion. When we 

 consider the total motions of the atoms of 

 the ball, even when it is shot from a can- 

 non's mouth, an inconceivably small change 

 of direction in the motion of every atom as 

 compared with the complexity of its path 

 would fully account for the flight of the ball 

 as projected by dynamite. 



Now we know of deflection and that it 

 arises from collision, and we know of no 

 other change in motion. Acceleration as 

 increase of speed cannot in the nature of 

 the case be demonstrated, for it may always 

 be explained as deflection, and can never be 

 explained without deflection; and to as- 

 sume acceleration as increase of velocity is- 

 to contradict the law that action and reac- 

 tion are equal and to afi&rm that motion can 

 be created and destroyed. 



If acceleration is explained as deflection,^ 

 it is explained by referring it to a known 

 cause and adequately explained. 



Let this argument be stated in brief : 



First, the tendency of modern investiga- 

 tion is to explain all forces as derived from 

 modes of motion. Great progress has been 

 made in this direction, and the theory is- 

 widely accepted. 



Second, all understood forces are collis- 

 ions. 



Third, if all forces are collisions the mo- 

 tions from which they result obey the third 

 law of motion, that action and reaction are 

 equal. By this law it is seen that no mo- 



