190 Dr Searle, A Simple Method of determining 
Hence, going as far as >d?, we find for the correcting factor 
ns 250 fo =a : 
FB = (=) Sg= (1+ St.) (14 = 14 528 » (19) 
~ ne \7 q n NO? 2° 
y| Yo %o NQ 
aS ora! 
q gtd qo — a 
and since g,+d and q,—d are both positive, 
Since 
1 Lig n 
Ys=S—]5G—)>S=. 
q Qo (Qo ) Yo 
2 S 72 
al ) (get + Sa) Bull a 
n 
Hence —(— -, 
TENGE Ngo” 
and thus / always exceeds unity. . 
To illustrate the practical application of the calibration cor- | 
rection, I give the data for the flow tube No. I used in the 
measurements described in § 7. The following table gives the | 
length g of a mercury thread in 11 equally spaced positions along | 
the tube; the length of the tube was 64°82 cm. 
Length of 5 1 ‘ 
isesd q i. q am @ 
! 
cm. cm.” Clee cm. em.” 
6°32 39-9424 0158228 —0:15 0:0225 | 
6-40 40-9600 0:156250 —0-07 0:0049 | 
6-40 40-9600 0:156250 — 0:07 0:0049 | 
6-38 40-7044 0-156740 — 0:09 0-0081 | 
6-40 40-9600 0:156250 — 0:07 0:0049 | 
6-43 41-3449 | 0155521 — 0-04 00016 | 
6-49 42-1201 0:154083 + 0:02 0-0004 
6°53 42-6409 0°153139 + 0:06 0:0036 
6°60 43°5600 0°151515 + 0°13 0:0169 
6°60 43-5600 0151515 + 0:13 0:0169 
6:58 43°2964 0°151976 +0-11 0:0121 
p= 6°47 Zq?=460:0491 = j= 101467 =d?=0-0968 
Hence, since n= 11, we find, by (18), 
1 1\?__ 460:0491 x (1°701467) 
=—d>_7 = — 
a md . 5) 18 3 
The need of tables giving g? and g™ to several significant 
figures may be avoided by finding # by formula (19). Thus 
33d? 3x 00968 | 
UA ee ere 
= 1:00068. 
