58 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 68 



An example will best show the method of using the formula. 

 Taking the case with a slit of 0.67 mm. linear width and subtending 

 in the spectrum an angular width equivalent to 0.05 mm. as measured 

 on the plate (equal to a) and a bolometer 0.5 mm. wide and sub- 

 tending 0.29 mm. (equal to ^) on the plate, then the formula becomes 



a^kJ(x)=F{x) -1/4- </)i(^)+o.o86(/)o(.r) 



= F(v) - I i F(x + smm)-F(x-3mm) _p(^.') 

 ^" "^ 4 [ 2 ^' "^ 



+ o.o86| '^^^-^' + 3^^)-^i <^-^'-3^>^^0 -d>,(^-) 

 [_ 2 ^ 



Table 15. — Example of the Application of the Formula for Correcting 

 FOR THE Finite Width of the Slit and the Bolometer 



The first step as followed out in table 15 was to read F(x), the 

 observed energy curve at every mm. Next ct^tix) was obtained by 

 subtracting, for example, the value of F(x) at .r = 3 from the mean 

 of the values at .^' = 3 — 3 or o and .t' = 3 + 3 or 6 and so on proceeding 

 down the column. 4>2{^') was obtained from <pi{x) exactly as was 

 (f>i(x) from F(x). The completion of the process is evident from 

 the headings of the columns, the final column giving the corrected 

 energy curve. 



