On the Origin of the Atomic Theory. 363 



The following is the demonstration above referred to.-<' lu 



the arc AB of a circle take a small part, Af(r;><. ^ 



AC, which suppose to be a straiglu Ime. ^, ^'" "^ \ ■» 



But if AC is a straight line, CB, which 



is equal to it, must be a straight hue. ; ] 



For the same reason 7i7??, which includes 



the point in which AC and CB are jonied, 



is also a straight line ; and therefore the . ", , , 



whole arc AB is a straight line, winch is evidently absurd. 



Therefore no part of a circle is a straight hnc—Q. L. U. 

 But let AC be a i)art of a regular polygon; then it is evident 



that all the conditions required by the 



above demonstration are fulfilled, and 



vet the figure is composed of straight 



lines.— Besides, when it is assumed 



that a circle is composed of small 



straight lines, the magnitude of each 



line Is supposed to be infinitely small 



when compared with that of the circle . . , 



of which it forms ^ part. Therefore the proposition does not 



appear to admit of 'a geometrical demonstration. Bu if such 



Tassumption be necessary in the investigation of heor ms 



there can be no good reason for rejecting it, unless it can be 



proved that no p^rt of a circle can be a straight line. 



June 5, 181G. ' * 



LXXV. 0?i the Origin of the Atomic Theory. By William 



HiGGINS. 



To Mr. Tilloch. 



Sm — You will oblige me and every lower of justice by in- 

 serting in your impartial Magazine the following rernarks on au 

 artcle^elafingtoti;ey/..,.ic7V.eo., yuiblishcdint^^.^^^ 

 part second, of the fourth and hfth editions of^'^^ ^ ^^ 

 Icedia Brilanmca, which article was written by Dr. 1 homson 

 ^ The Doctor commences by stating, that the most eminen of 

 theGreek philosophers supposed the ultimate elements of matter 

 ocoiisistlf aton\s or pLlticles incapable ot further division o 

 diminution; and that this doctrine was ",'i«P^'-^\'^y .^J ^^^ 

 Newton, and In- manv celebrated philosophers since lis time 

 Th i peifectll correct ; but they had not the most f staiU idea 

 of its application to chemistry in the sense m which 1 had taken 



'' The Doctor proceeds by giving a sketch of the V'^^^J^ 



