'produced by a Fluid in Motion, 



115 



Time of taking 

 the tempera- 



Water at 6° C. 



Methvlated alcohol at 6°-5 C. 







* 





ture from the 

 commence- 



















ment of heat- 



Upper ther- 



Lower ther- 



Upper ther- 



Lower ther- 



ing. 



mometer. 



mometer. 



mometer. 



mometer. 



minutes. 











10 



11 75 C. 



1200 C. 



16-25 C. 



16-50 C. 



20 



1700 



1750 



23-25 



23-50 



30 



21-25 



22-50 



28-50 



2900 



40 



25-00 



26 25 



3200 



32-50 



50 



28 50 



3000 



34-75 



35-25 



60 



31-25 



32-50 



36-50 



37-25 



It is seen from the above that a uniform temperature was very 

 rapidly acquired by both liquids, the greatest difference in tem- 

 perature between the uppermost and lowermost layers of water 

 amounting to only l o, 50 C, and in the case of the alcohol to 

 only 0°-75 C. 



In making the experiment with the sphere of oil, it will be 

 borne in mind that a mixture of alcohol and water was employed, 

 and that the oil-sphere floating therein was brought to its de- 

 sired position by pouring a small quantity of alcohol into the 

 mixture as soon as the sphere had come to rest. It was there- 

 fore thought to be advisable to ascertain the rapidity with which 

 the mixture acquires a uniform temperature, and to what extent 

 this result is retarded by the addition of a known quantity of 

 alcohol. » 



In order to determine this, a mixture was made of 500 cub. 

 centims. of water at 4 0, 5 C. with 500 cub. centims. of methyl- 

 ated alcohol at 6° C. The resulting mixture (care being taken to 

 make it perfectly uniform) was found to occupy a volume of 

 980 cub. centims., and to possess a temperature of 14 0, 25 C. 

 It was allowed to cool down to 7° C, and then heated for an 

 hour, under the same conditions which obtained when each 

 liquid was heated separately, the temperatures being noted at 

 similar intervals. At the end of the hour it was cooled to 

 7° C, and 50 cub. centims. of alcohol at 8° C. were poured 

 in, and the heating recommenced. The added alcohol was 

 coloured by means of a minute quantity of roseine, in order that 

 the depth to which it penetrated might be observed. (It is need- 

 less to remark that the tinctorial power of roseine is so great 

 that the amount added could not affect the accuracy of the ex- 

 periment.) Although the alcohol was poured into the mixture 

 (already containing half its bulk of that fluid) from a height of 

 40 or 50 millims., it showed no tendency to mix readily : the 

 great bulk of it (as shown by the amount of colour) remained 



12 



