498 



Mr. C. G. Darwin on the Collisions of 



from the experiment described on p. 554, which deals with 

 the flat part of curve A. With our definition of p instead 

 of p, the calculation on p. 555 stands good, and we thus 

 have as the absolute scale /7=2'4xl0" 13 cm. for the value 

 of p on this flat part. 



Jn the curves of p. 550 the fastest H-particles at every 

 range have very nearly four times the range of the exciting 

 a-particles. This is the confirmation, referred to above, of 

 the law we have assumed for the loss of velocity of H-particles. 

 For the reduction the longest range at which scintillations 

 were seen was taken as Ar. The abscissa of a point on the 

 curve is its t. Rutherford measured these quantities in their 

 equivalents in cms. of air, not as we have done in hydrogen, 

 but this will not affect the ratio tjir. From the values of 

 t\kr we get O — A 1 by means of the table. These are to be 

 associated with values of p proportional to the square root 

 of v. The value of the second differential was tested at the 

 point of greatest curvature in A, and it was found that the 

 ^resulting correction was negligible. 



Fis-. 4. 



>S 10° 20° 80° 40° 



Experimental Collision .Relation (p, 6). 



p is measured in units of 10 ~ 13 cm. Each curve, as determined from 

 experiment, ends at the point marked by a short cross line. H is 

 the curve given by the collision of point charges, when a has the 

 same velocity as in E. 



The curves of fig. 4 are the results of this analysis. The 

 curve H is the theoretical curve for point charges of the 

 snme velocity as F. It would appear from the uneven way 

 in which the curves are arranged, that there are some errors 



50" 



