106 Proceedings of the Royal Society of Victoria. 



on some clays the observations would be in much better agree- 

 ment than on others. Another source of error, and one which 

 eluded pursuit for some time, was due to allowing any parts of 

 the apparatus inside the calorimeter to be in contact, especially 

 the thermometer bulb and the glass spiral or the wall of the 

 calorimeter ; errors due to this cause frequently amounted to 

 2 or 3 per cent., and it is a little difficult to see why this should 

 be the case. One further reservation must be made — the 

 experiments here described were made with a view of testing the 

 method of working, and all that was desired was a series of 

 mutually agreeing results, the absolute accuracy being of much 

 smaller importance for this purpose. Consequently it was not 

 thought necessary to standardise the thermometers by direct 

 comparison with the air thermometer, but this will have to be 

 done before actual results can be obtained. 



With all the above sources of difficulty and error in view, it 

 does not seem too much to say that for very accurate thermal 

 measurements a mercurial thermometer is unsatisfactory, and 

 that the electrical-resistance thermometer will have to be em- 

 ployed, and with it a much greater degree of accuracy, perhaps 

 even to 1 part in 4000 or .5000 may be attained. 



The various weights required were very simply determined, 

 but even here the attainment of the greater accuracy was 

 hindered by the fact that the Physical Laboratory of the Mel- 

 bourne University, where these experiments were carried out, 

 did not possess an accurate balance large enough for the pur- 

 pose, and the balance used was not only rather heavily strained 

 by the load but was not under favourable conditions for sen- 

 sitiveness. The only point requiring special reference is the 

 determination of the weight (Wj) of the hot liquid. This is 

 found by weighing the calorimeter and apparatus together with 

 its contents before and after the experiment ; the increase of 

 weight was then the weight of hot liquid that had actually 

 entered the glass spiral, free from all assumptions as to how 

 much remained in the tube in the hot jacket or similar un- 

 certainties. 



One very important advantage of this method is the ease 

 with which the experiments on any liquid can be repeated under 

 similar conditions, so as to check the experimental work in 



