2(5 
PEOF. H. L. CALLENDAR ON THE VARIATION OF THE SPECIFIC 
It was found on reducing the above observations that insufficient time had been 
allowed for the conditions to become steady after changing the flow from 10'47 to 
7‘43 gr./sec. A change of 0°’016 C. occurred in after the first pair of readings at 
Q = 7'43. All the readings have been included in the mean, hut, if the first pair had 
been rejected, the heat-loss would have djeen I‘50 for this flow. The signs attached 
to the temperatures are those taken in finding the sum ZC The values of Zd/^ were 
taken from the curve given in fig. 6, representing my formula (lO). The values of 
the heat-loss X deduced are nearly the same for all the flows. It should be observed 
that the heat-loss, IffiO cal./sec., is less than 0'5 per cent, of the heat-exchange, 
325 cal./sec., for the large flow, and that the flow could easily be varied in the ratio 
of I to 8. In the continuous-electric method with a vacuum-jacket, the heat-loss at 
92° C. amounted to 4 per cent, of the maximum watts, or 10 per cent, of the 
difference between the flows, on which the result depends. In Reyxolds and 
Moorby’s experiments the heat-loss amounted to 5 or 10 per cent, (with or without 
lagging) of the difference of the loads in the heavy and light trials. In neither case 
could the flow be varied satisfactorily in a ratio greater than about I to 2. The 
continuous-mixture method is undoubtedly preferable to either in this respect, 
since it permits a wider range of variation of the flow, and a greater reduction in the 
heat-loss. The agreement of the values of the heat-loss deduced from the different 
flows by means of foi’inula (lO) is closer than might have been expected, because 1 in 
the last figure of the heat-loss corresponds to 0°‘001 C., or 1 in 30,000 of the heat- 
exchange for the large flow. It may be said that formula (lO) is verified to at least 
1 in 5,000 for the ratio of the mean specific heat from 69° C. to 100° C., where it 
differs most widely from Ludin’s, to the mean specific heat from 25° C. to 56° C. 
Formula (lO) gives 1'0050 for the ratio. Ludix’s formula gives I'OIOI, differing by 
0‘54 per cent. If Ludin’s formula had been employed for the reduction, the heat- 
loss, instead of being nearly the same for the different flows, would have appeared to 
vary from 3‘38 for the largest flow to 1’79 for the smallest flow. The heat-loss 
should, as a matter of fact, have been slightly less for the large flows than for the 
small, because the rise of temperature of the jacket J with the smallest flow was 
rather more than sufficient to compensate for the fall of mean temperature of the 
thermometer-pockets. 
Seeing that the results of the continuous-electric method have now been so closelj^ 
verified by the continuous-mixture method, which is independent of electrical energy 
measurements, it would appear to follow that the discrepancy of I per cent, at 80° C. 
between these methods and those of Messrs. Bous field and Ludin is to be attributed 
mainly to fundamental differences in the thermonietric and calorimetric methods 
employed. In my continuous-flow methods the troublesome and uncertain corrections 
of mercurial thermometry at temperatures between 40° C. and 100° C. have been 
avoided, and a higher order of accuracy in the temperature measurements has been 
secured by the direct employment of platinum thermometers. Errors due to lag, or 
