PORCELAIN AIR THERMOMETRY. 
229 
(H/h) must be derived from the general equation, which, after differ- 
ltiation, is simplified by inserting H=h. 
If into these equations we introduce mean values, such as /=20°, 
=20o 7 ^=0.00367, /?=0.000017 ; if, moreover, we insert for — * the 
dues which may be taken from Tables 58 to GO, above, then the said 
[uations lead to the following tabular comparison. It is expedient in 
Idition to the absolute values of the divers errors dt, ST h 6V U oV, 
, da, Sft, 6.H, SM, 6S, which individually influence the result by 
1000, to give also the relative values of some of these quantities, or 
fain the error of the ratios, viz : 
6 ft 
d (r)' 'CO' *(?)? *(*)/*.«»**(«>/* 
Table 76. — Comparison of divers errors which affect the result one pro mille. 
From this table of errors a fully satisfactory inference of the value 
the experiments made can be obtained. 6 M and 6 8 and their rel- 
ive values are primarily of interest. ,They indicate the degree of 
ecision with which the logarithmic calculations must be made in 
der that the arithmetical operations may be consistent with the 
curacy of the experimental data. 6 M, however, has further im- 
Ttance, inasmuch as this factor enters into most of the formula' for 
rors. By far the greater number of these may therefore be made 
3re elegant and more practically serviceable by introducing 6 M in the 
inner shown on page 229. 
Regarding the introductory measurements v the volume of the bulb 
&t the fiducial temperature it appears that the volumetric method 
? the estimation of v described on page 214 is acceptable; for by cau- 
)us work with all parts at the same temperature a mean correct- 
($83) 
