162 



Capt. W. de W. Abney on 



[Mar. 7, 



quinine sulphate, whilst another was exposed to the full action of the 

 unshaded light. The times of exposure varied between one and ten 

 minutes. The intensity of the actinism was measured by Roseoe's 

 method, which need not be described. The curve obtained from the 

 paper exposed behind the quinine cell is practically identical with that 

 obtained optically from the blue components when any one point in 

 the former curve is made to correspond to a point in the latter which 

 has the same abscissa. The following Table gives the results of the 

 experiments made with this particular machine. The numbers or letters 

 in the first column refer to the numbers in the diagram. The horse- 

 power given is the total horse-power recorded less that required to 

 drive the machine with the brushes up. 



Expenditure of H.P. 

 Table I refers to Diagram I. 



No. 



Revolu- 

 tions. 



H.P. 



a 



240 



10 



b 



308 



1-6 



c. .. . 



350 



2 5 



d .... 



400 



3-8 





460 



5 6 



f 



480 



5 7 



9 



520 



7-9 



h 



550 



8 5 



h 



565 



9 



Integration of Blue Light. 

 Table II refers to Diagram II. 



No. 



Revolu- 

 tions. 



Candles. 



1 



240 



360 



2.. .. 



308 



660 



3 



350 



750 



4.. .. 



425 



1,700 



5.. .. 



460 



2,500 



6.. .. 



490 



3,000 



7.... 



520 



4,860 



8.... 



550 



4,800 



9.. .. 



565 



6,500 



10. . . . 



580 



6,000 



11.... 



600?* 



10,100 



Integration of Red Light. Integration of Actinic Power. 



Table III refers to Diagram II. Table IV refers to Diagram II. 



No. 



Revolu- 

 tions. 



Candles. 





No. 



Revolu- 

 tions. 



Candles. 



12.... 



240 



180 





21 



350 



890 



13. . .. 



308 



280 





22. . . . 



460 



2,750 



14. . . . 



460 



860 





23.... 



560 



9,000 



15.. .. 



500 



1,080 





24. . . . 



580 



10,050 



16. . . . 



520 



1,300 





25.. .. 



600? 



11,020 



17. . . . 



540 



1,620 









18. . . . 



575 



1,520 











19.. .. 



580 



2,100 









20. . . . 



600? 



2,400 









* A ? is placed against the 600 revolutions, as the engine at that velocity worked 

 somewhat unequally. 



