U0 I)K . F, H. 1MFFITHS AND MR. FJ5ER GRIFFITHS OX THE 



Two series of experiments with copper at C. were performed under precisely the 

 same conditions, except that the lid with the lighter tubes was employed in the first, 

 and that \\ith the heavier, in the second, series. 



ra the differences in the capacity for heat resulting from these two series, the 

 dim-rence in the amount which had passed into the quartz tubes could be determined, 

 the capacity of the alloy, solder and copper, being known. Let m^, and m.^ be the 

 respective quartz capacities. Then, from the experimental results we found 



m l , = l'37; TA - 2'28. 



No doubt, a temperature gradient existed along these tubes, but the value of sm 

 thus obtained gave the " effective" capacity, i.e., the number of calories which flowed 

 into the quartz tubes as the temperature of the block was raised by 1 C. 



A comparison of other experiments at C., where the conditions were similarly 

 altered, indicated that the accuracy of this " quartz correction " was sufficient. 



4. Heat Absorbed by the Air Within the Brass Vessel. 



As stated in Section II. we were able to measure the average increase in pressure, 

 and therefore in temperature, of this air during an experiment. The volume being 

 approximately 1500 c.c., the average rise of pressure was 07 mm. Hg, indicating an 

 increase of temperature of 0'2G C. The number of calories thus expended equals 

 0'08. 



As the average heat supply during an experiment was about 400 calories, it is 

 evident that this correction would not amount to more than 1 part in 5000 ; we did 

 not consider, therefore, that the accuracy of our experiments necessitated the inclusion 

 of this correction, especially as it could be only roughly determined. 



SECTION VII. 

 Mass and Density of the Metals. 



The masses of the blocks varied from 1 to 4 kgr. The balance used for the larger 

 masses was capable of weighing to O'Ol gr. ; masses under 100 gr. were determined 

 by a Verbeek short-beam balance. The method of double weighing was used and a 

 correction was applied for the displaced air. 



A calibration of the box weights proved that, relatively, they were correct to a 

 high degree of accuracy; as, however, the absolute values were required, the 2 kilos. 

 (from another box), and the 1 kilo, and 100 gr. from this box were forwarded to the 

 National Physical Laboratory for standardisation. The kilogram and the 100 gr. 

 weights of our box were found to be exact and the correction on the 2 kilos was 

 given as + 0'29 gr. 



