the Healing of a Disk by rapid Rotation in vacuo. 225 

















t^ . t» 





S3 r- 



6*9 



3* 



°£ 



Heat indication. 







urit 



bso- 

 ega 



1 



*Z 



£ * 





Nature 



Tension 



© cLi • 



O 



d 



No. of 

 tions i 

 set. 



Time a 

 speed, 

 conds. 



No. of 

 handle 

 speed. 



Divi- 

 sions. 



Fahr. 



of gas. 



of gas, in 

 inches. 



? ^ "3 n 



VTL 



2 



30 



22 



22-51 

 233/ 





hydrogen 



0-6 



95 



VIII. 



3 



30 



22 





air 



0-7 





IX. 



2 



30 



20 





0°-95 



hydrogen 



05 



97 



X. 



2 



30 



20 





0°-87 



air 



1-1 





XI. 



3 



30 



20 





0°-85 



hydrogen 



025 



98-5 



XII. 



3 



30 



20 



... 



0°-8G 



coal-gas 



025 



95 



(4) It may be objected to (2) that the greater heating effect 

 from a blackened aluminium disk than from an unblackened one 

 does not prove that this heating effect may not be due to air, since 

 the blackened surface may be imagined to lay hold of the air more 

 than the metallic one. But the following sets of experiments prove 

 that the heating effect of the aluminium disk with both sides black- 

 ened is the same as when only one side is blackened. 



o 

 d 



No. of ob- 

 servations 

 in each set. 



Time at full 

 speed, in 

 seconds. 



No. of turns 

 of handle 

 at full 

 speed. 



Heat in- 

 dication, 

 in ° Fahr. 



.2 -~ 



'S3 S3 



3° 





X. 



XIII. 



2 



3 



30 

 30 



20 

 20 



09 



0-8 



1-1 

 04 



Disk blackened on one side. 

 Disk blackened on both sides. 



It would therefore appear to be proved that in these experiments 

 the heating effect is due to the increased temperature of the disk. 



1 7. Before proceeding further it may be advisable to detail some 

 experiments made with an ebonite disk -^ inch thick. In these 

 experiments care was taken that the ebonite should have the same 

 temperature throughout its thickness, so that there might be no flow 

 of heat from the interior to the surface, or vice versa. The experi- 

 ments were made with rock-salt in the cone. 



© 



GO 



O 

 O 



No. of obser- 

 vations in 

 each set.- 



Time at full 

 speed, in se- 

 conds. 



No. of turns 

 of handle at 

 full speed. 



Heat indica- 

 tion, in divi- 

 sions. 



Nature of 

 gas. 



Tension 

 of gas, in 

 inches. 



Probable puri- 

 ty of gas (ab- 

 solutely pure 

 gas = 100). 



XIV. 



3 



30 



20 



32 



air 



11 





XV. 



1 



30 



20 



30 



air 



026 





XVI. 



1 



30 



20 



31 



air 



11 





XVII. 



2 



30 



20 



28-5 



air 



0-26 





XVIII. 



2 



30 



20 



28-5 



air 



025 





XIX. 



3 



30 



20 



29 



hydrogen 



0-25 



90 



Phil. Mac/. S. 4. Vol. 33. No. 222. March 1867. Q 



