338 
PROFESSOR O. REYNOLDS AND MR. W. H. MOORBY 
Whence, since g has dimension (LT ~), 
27rNRW _ C 
where the dimensions of Qlg are 
Tlie object in this research being to replace the standard of temperature, as defined 
by the scale on a particular thermometer, by the standard obtained from the states 
physically defined by melting ice and by water boiling under a standard pressure, ^is 
here defined to express this interval, and S is, in accordance with the definition already 
given, used to express the ratio which the heat required to raise unit mass over any 
interval, per degree of rise, bears to that required to raise pure water over the 
interval d, per degree of rise. 
The Standards Involved. 
39. It appears from the dimensions of Gig, as obtained in the last article, that the 
only general standards to which reference need be made are those of length and 
temperature. 
It is, however, to be noticed that the determination of the wmrk and the heat 
involve the determination of separate masses, and that the units only disappear on 
the condition that they are equal. 
The Measurement of Mass. 
40, Since it was not necessary to refer the mass to a general standard, the 
weights used were only referred to a Board of Trade standard for convenience. 
Thirteen of the 25 lb. weights used for loading the brake were adjusted to the 
Board of Trade weight, then carefully balanced against each other, till, balanced in 
groups of four in any arrangement, there was less than O’Ol lb. difference. Four of 
these weights were then taken as the standard. 
The compound lever machine, which had two scales on the same lever, one notched 
to each 100 lbs. for the position of the large rider, the other with a flat scale for 
every 1 lb. for the position of the small rider, wms taken to pieces and the knife 
edges re-ground and re-set (by Mr. Foster) till consistent results were obtained to 
the one-hundredth of 1 lb. Another rider wms also made to work on the same scale 
as the small rider, being adjusted to one-hundredth of the weight, so as to read 
0-01 lb. 
The scales were then carefully surveyed by the standard 100 lb. weight, the 
original small rider being adjusted till the difference between its extreme positions 
on the scale balanced the standard to < O'Ol lb., and the corrections for each V-notch 
into which the feather on the large rider fitted ascertained by balancing the standard 
to a like degree of accuracy. 
