114 
MARVIN. 
“ (Note. —Tlie gas thermometer would still remain the ultimate or 
theoretical standard, and the exact relation of the British Association 
scale to the absolute scale would be the subject of future investigation. 
In the present state of experimental science, the difference between the 
two scales over the greater part of the range is less than the probable 
errors of measurement with the gas thermometer, and the possible accu¬ 
racy of measurement with a platinum thermometer, especially at high 
temperatures, is of a much higher order than with the gas thermometer. 
Measurements directly referred to the British Association scale would 
therefore be of greater permanent value, because they could be subse¬ 
quently corrected when the relation between the scales had been more 
accurately determined.) 
“(3.) That the value of the difference coefficient d in the parabolic 
difference formula be determined for the British Association standard 
thermometers by reference to the boiling point of sulphur as a secondary 
fixed point in the manner described by Callendar and Griffiths, ‘ Phil. 
Trans., A, 1891.’ 
“ (Note. —It is probable that this method gives the best results over 
the whole range of temperatures above -100 C. At very low temperatures 
there appear to be singularities in the resistance variation of metals 
which require further investigation. The boiling point of liquid oxygen 
would be a more convenient secondary fixed point to choose for low- 
temperature research, especially for testing thermometers, the construc¬ 
tion of which did not permit their exposure to a temperature as high as 
that of boiling sulphur.) 
“ (4.) That the temperature of the normal boiling point of sulphur 
under a pressure of 760 mm. of mercury reduced to 0 C. and latitude 45° 
be taken, for the purposes of the British Association scale, as 444°.53 C., 
as determined by Callendar and Griffiths ( loc.cit .) with a constant pressure 
air thermometer. 
“ (Note. —Until the relation between the various gas-thermometer 
scales and the expansion of glass and porcelain have been more accu¬ 
rately determined, it does not appear that anything would be gained by 
changing this value, to which so much accurate work has already been 
referred).” 
The Electrical Standards Committee, to which the ques¬ 
tion was referred, “appointed a subcommittee to consider 
details and report progress next year.” 
Before the close of the meeting the subcommittee had de¬ 
cided that platinum thermometers shall be constructed of a 
selected sample of platinum wire and be used as standards 
for high-temperature measurements. The selection of the 
wire is still under the consideration of the committee. 
