176 T. S. Taylor — Retardation of " Alpha RaysP 



ionization of the air in the chamber produced" less than 0'04 cm 

 deflection. This is so small as to be practicably negligible. 

 But had it been larger it would have made no difference ; 

 because it would have the effect of shifting all the curves in 

 figure 3 to the right by an equal amount, thus not changing 

 their relative positions or forms. 



Column 1 in Table I contains the distance in centimeters of 

 the sheet from the polonium. Column 2 gives the range in 

 centimeters of the a particle when entering the sheet. In 

 column 3 are given the air equivalents in centimeters of the 

 sheet corresponding to the distances in column 1 and the 

 ranges in column 2 as determined when the polonium was set 

 at 3*l cm from the ionization chamber. Columns 4, 5, 6, 7 and 

 8 contain the same quantities as column 3, as determined 

 with the polonium at 2*9, 3*0, 3*1, 2*8 and 3'0 cm respectively 

 from the chamber. 



Table I. A An. 



Distance 

 from pol- 

 onium to 

 the sheet 



Eange of 

 entering 

 particle 



3-1 



2-9 



3-0 



3-1 



2-8 



3-0 



Means. 



0-6 



3-17 



0*635 



0-635 



0-635 



0-635 



0-635 



0*635 



0-635 



0-8 



2'97 



0-626 



0-628 



0-629 



0-626 



0-629 



0*630 



0-628 



1-0 



2-77 



0-619 



0-620 



0-622 



0-618 



0-621 



0-623 



0-621 



1-2 



2-57 



0-613 



0-614 



0-616 



0-611 



0-613 



0*616 



0-614 



1*4 



2-37 



0-606 



0-609 



0-608 



0-603 



0605 



0-609 



0-607 



1-6 



2-17 



0-600 



0-601 



0-600 



0-596 



0-595 



0-601 



0-599 



1-8 



1-97 



0*592 



0-595 



0-592 



0-589 



0-584 



0-592 



0-591 



2-0 



1-77 



0-582 



0-581 



0-582 



0-579 



0-574 



0-581 



0-580 



2-2 



1-57 



0-572 



0-567 



0-571 



0-569 



0-564 



0*570 



0-569 



2-4 



137 



0-556 



0-548 



0-555 



0-556 



0*557 



0-552 



0-553 



The last column contains the average values of the six pre- 

 ceding columns. The agreement between corresponding quan- 



Table II. 



I 



II 



III 



IV 



Metal sheets 



Thickness in cms. 



Air equiv. in cms. 



Eatio 



A Au 



0-000127 



0-635 



4-99 X10 3 



B Au 



0-000174 



0-857 



491 X10 3 



A Pb 



0-000284 



0-923 



3-24 X10 3 



B Pb 



0-000411 



1 231 



3 01X10 3 



A Sn 



0-000386 



0-886 



2-29X10 3 



B Sn 



0-000799 



1-800 



2-25 X 10 3 



A Al 



0-00033 



0574 



1-74X10? 



B Al 



0-000612 



1-04 



1-70X10 3 



A Ag 



0-000223 



0-676 



3-03 X10 8 



