Defermininr/ the Specific Heat of a Liquid. JOl 



at one end at an approximately constant velocity and constant 

 temperature. At both upper and lower end, as close as possible 

 to where the pipe became immersed in the water of the calori- 

 meter, a thermometer was inserted; the temperature of the calori- 

 meter was I'ead by the same thermometer as had been used in the 

 previous method ; the same stirrer was also used, but now driven 

 by a water-motor running 300 to 400 revolutions per minute. 

 Everything having been working for some time, the experiment 

 consisted in catching and then weighing the quantity of water 

 running through the lead spiral while the temperature of the 

 calorimeter rose through a given range, say 4°C., the temperature 

 of the in- and out-flowing stream being noted at equal intervals of 

 rise of temperature of the calorimeter, viz., at every tenth of a 

 degree. The results obtained from this rough apparatus were so 

 encouraging that I proceeded to construct a better apparatus. The 

 "nest" of calorimeters was again used, but the innermost one was 

 discarded and the next largest used as the calorimeter ; it had a 

 capacity of about 400 to 500 cubic centimeti'es, and had two metal 

 vessels and two air-spaces as a protection from radiation and 

 convection on sides and bottom ; but by the new method the top 

 could be protected also, and this was done by two sheaves of cork 

 about three-eighths of an inch thick and leaving an air-space of 

 about one-eight of an inch between theni. In these corks 

 suitable holes were cut to just admit the thermometer, the spindle 

 of the stirrer and the ends of the spiral tube. This latter 

 proved nmch the most difficult part of the apparatus to obtain. 

 Properly such a spiral tube should be made of silver or platinum 

 with glass ends, but such a thing was not to be obtained in 

 Melbourne, and circumstances did not permit of my delaying the 

 experiments until I could have obtained a spiral from England ; 

 consequently I had to fall back on glass tubing as a substitute. 

 My first spiral was made for me by a ^Melbourne glass-blower, but 

 later on I succeeded in making them myself, though at no small 

 expense of shattered glass. From many points of view, however, 

 glass is not suitable to this purpose, partly on account of its 

 fragility and also because its conducting power is small ; but beyond 

 this there seems to be a tendency for the liquid in the calorimeter 

 to stick to the glass far more than it does to metal and so to hinder 

 what is of the greatest importance in a calorimeter — a free and 

 uniform circulation. 



