﻿Convective Cooling in Fluids. 933 



still greater heating (10° (J.) two oscillations were noticed, 

 a maximum being reached in \ minute followed by a 

 minimum f minute later, from which the temperature 

 then rose to its final value. These oscillations resemble 

 those of a damped system, l he three stages due to different 

 degrees of heating corresponding to three different degrees 

 of damping. The phenomena cannot be attributed to the 

 galvanometer, and must have their origin in the liquid 

 convection currents set up, for the galvanometer normally 

 reached its final deflexion in a few seconds, whereas the 

 observed variations occupied minutes. 



Results. 



The results obtained are given below in tables compiled 

 from smooth curves through experimental points, this making- 

 it possible to give them much more concisely than would 

 otherwise have been the case. 



It is necessary to state that, in general, results were 

 reproducible to within 5 per cent. With respect to repro- 

 ducibility, the glycerine series was least satisfactory, but 

 this may have been due to its extremely viscous nature and 

 to the very rapid manner in which its viscosity changes 

 with temperature. 



In Table III. results are given for the various liquids, 



Table III. 

 Relation between 10 4 H and 6. 



[Heat loss (H) in calories per cm. length per ° C. excess temperature.] 









Temperature excess 



(0)° C. 





Liquid. 



Wire 

 diam. 



gd acjk. 











1. 



2. 



5. 



10. 



20. 



50. 



Gases* 



0-0083 

 0-0155 



4-74xl0- 5 

 3-09x10-* 





0-82 



0-83 

 0-99 



0-86 

 103 



0-91 

 1-10 



103 

 1-23 



Toluene 



0-0083 

 00155 



0-624 

 4-06 



9-8 



8-6 

 107 



95 

 121 



10-4 

 136 



111 

 15-4 



12-6 

 18-2 



CCL, 



0-0083 

 0-0155 



0920 

 5-98 



6-3 



8-1 



6-8 

 9-1 



7-7 

 10-5 



8-4 

 11-7 



: 9-2 



12-9 



103 

 14-9 





Aniline 



00083 

 00155 



0-782 

 5-08 



7-5 

 9-9 



8-4 

 110 



9-6 

 123 



10-8 

 14-1 



12-1 



16-2 



14-6 

 194 



; Olive oil ... 



00083 

 00155 



0472 

 3-08 





5-3 

 68 



61 



7-6 



6-7 



8-7 



7-4 

 99 



8-6 

 120 



! Glycerine ... 



0-0083 

 00155 



0-343 

 2-23 





96 



9-9 



9-4 

 107 



95 



119 



] 10-3 

 135 



162 ! 



* For gases 9 was varied up to 200° C, and the values of 10 4 H obtained for 

 the two wires at = 200° C. were T34 and 1'60 respectively. 



