Vol.. 6, 1920 
PHYSICS: DUANE AND STEN STROM 
479 
The tips of the peaks in these curves correspond to the Hnes in the 
characteristic X-ray spectra. It is possible to determine with certainty 
between which two settings of the crystal a peak lies, and also about how 
far from each it is. This means that, when the apparatus is functioning 
well, the grazing angle of incidence can be estimated to within about 7" 
/2 
II 
10 
9 
" 8 
\ 
X 
1: 
/ 
1 1 1 1 1 1 
1 
; 
<-RAY 5P5CrRA OF TUNGSTEN 
1 
-8 
- 7. 
Sth Ord 
er Sped rum 
3rd Ord Spec f rum 
/SI ~k 
55' 5" 
60,^= 5° 55' 40 
0p':r 5° 14' 8 
• 
- e 
-5 
- 4 
'A 
— jr«' 
II 
+ 
+ 
V 
/ 
+ 
\ 
= 5° 5' 23 
II 
J 
-♦- — 
oc, 
-1 
—0 
Ja 
n.9ih 
^3. 
40' 45' 50'^ 
278'' 
0' 35' 40' 
298° ^ 
++■ - 

3rcl Order S 
'pec 
i'run 
n — 
1 
- 
aC 
2 
•3- 
■\ 
Y 
\ 
1 
4 
— H 
ft 
A- 
1 
-\ 
+ 
p 
V 
1 — ^ 
-r 
1 
Ma 
rch 6fh 
March 4fh 
feh.24ih 
March 4ih 
Afcf/ 
rh 8i-h 
45' 50' 5 
282° 
1 1 
5' 0' 5' 
283° 
J 
40' 45'- 0' 5' 10' 1 
283° 294° 
Crt^sial Table Anq/es 
t i ^ J \ \ ! 
5' 
SO' 55' 
294° 
^ J L ^ 
0' 5' 
295° 
^-J \ 
FIG. 2 
of arc. For the tungsten K series the grazing angles of incidence in the 
first order spectrum amount to about 2° = 7200", and, therefore, the 
error in a satisfactory determination of a wave-length ought not to ex- 
ceed Vio, V20, V30, V40, etc., per cent in the spectra of the first, second, 
third, fourth, etc., orders, respectively. 
