104 Proceedings of the Royal Society of Victoria. 



its upper end projects through a hole in the lid of the tin vessel. 

 This end is closed by a cork, and through a hole in this cork 

 passes the stem of a delicate thermometer graduated to tenths 

 of a degree Centigrade. At its lower end the glass tube 

 contracts to the same bore as that of the glass spiral in the 

 caloriTueter and passes out through the rubber stopper (c). 

 This stopper is about half an inch thick, and the glass tube 

 ends about half way through it. This end of the glass tube 

 is slipped into the end of a rubber tube, which is left projecting 

 outside for about three inches ; a pinch-cock, made of two pieces 

 of wood so as to release very suddenly, grips the rubber tube just 

 as it leaves the stopper — while the liquid is in the hot jacket, 

 this is, of C(iurse, closed. The object of this arrangement is to 

 ensure that all the contents of the "hot" tube shall be at the 

 jacket temperature, and the pinch-cock contracting the rather 

 stijEf rubber tulje up to the point where it is slipped over the 

 glass tube and so holding all the hot liquid well within the jacket. 

 This arrangement is further preferable to a stop-cock on account 

 of the speed and certainty with which it can be manipulated, 

 and this is of importance, as it reduces any loss of heat by 

 radiation during the passage of the liquid along the inch or so 

 of rubber tubing used to connect the tube in the jacket with 

 the spiral tube in the calorimeter at the instant of making the 

 experiment. When it is desired to use as the " hot " liquid any 

 substance such as benzine which would attack the rubber tubing 

 this arrangement could not be used, but a suitable quick-acting 

 glass stop-cock could no doubt be obtained. 



The water-jacket being kept warm by means of a gas-jet 

 placed below it, there was a possibility of considerable difFei'ences 

 of temperature existing between various parts of the jacket-water, 

 and it was thought that a mechanical stirrer would have to be 

 used, but it was found that with everything in steady work the 

 temperature changes were so very slow and the differences of 

 temperature in various parts of the jacket so inappreciable that 

 stirring was unnecessary ; shifting the thermometer bulb from 

 the highest to the lowest portion of the hot liquid in the glass 

 tube produced no visible motion of the mercury, and it was 

 therefore assumed as sufficiently accurate to take the reading of 

 this thermometer as the mean temperature of the hot liquid. 



