1887.] On Photometry of the Glow Lamp. 253 



TaKe I. — A Wood house and Rawson lamp, changing the resistance 

 and reading current and potential. 



c. 



P. 



Watts x 

 a constant. 



Aperture 

 of disk. 



Calculated 

 aperture 

 (shadow) . 



Calculated 

 aperture 

 (grease-spot).* 



13 4 



38-0 



509-2 



180 



180-23 



181-6 



12-75 



36'1 



460-3 



135 



135 -20 



134-2 



12-5 



35-5 



443-8 



120 



121 -44 



120 -0 



12-3 



350 



430-5 



110 



110-95 



109 -4 



12 2 



34-7 



423-3 



105 



105 -47 



105 5 



11-9 



33-8 



402-2 



90 



90:11 



91*1 ! 



11-7 



33-1 



387-3 



80 



79-99 



80 1 



11-5 



32 -5 



373-7 



70 



70-34 



71-2 



11-2 



31-7 



353 -9 



60 



60 20 



613 



10*9 



30-75 



335 -2 



50 



49-40 



48-7 



10-6 



29-9 



316-9 



40- 



40 -42 



39-8 



10 -2 



28-8 



293-9 



30 



30-11 



29-7 



9-65 



27-55 



265-4 



20 



20-07 



19-5 



9-35 



26-7 



249-6 



15 



15-07 



15 



9-0 



25 6 



230-4 



10 



10-09 





8-4 



24-2 



203 3 



5 



. 



4-75 





m = 144. n = 27 "2. 



Table II. — Swan lamp-light measured by changing the resistance and. 

 reading current and potential. 



c. « 



P. 



Watts x 



Aperture of 



Calculated 



a constant. 



disk. 



aperture. 



23 -2 



24-2 



562-4 



180 



180 -63 



22-0 



22-2 



488-4 



133f 



132 -71 



21 6 



21-6 



466 -6 



120 



119 -89 



21-4 



21-4 



458-0 



115 



114-91 



20'6 



19-9 



410-0 



90 



89-14 



20-2 



19-2 



387-8 



79f 



78-68 



19-7 



18-7 



368 -4 



70 



69 -88 



19-2 



18 



345-8 



60 



60-37 



18-6 



17-2 



320-0 



50 



50-00 



17-9 



16 3 



291 -8 



40 



40-25 



17 -1 



15-3 



261-6 



30 



30-8 



15 -9 



13-8 



220-4 



20 



19-98 



14 3 



12 



171*6 



10 



10-11 



13 -0 



10-6 



137-8 



5 



5-29 



m = 50'52 n = 38-0. 



The following shows the readings in full of one set of observations : — 



* This column shows results given by the grease-spot method. The watts are 

 not given, but merely the results, to enable a comparison to be made between the 

 accuracy of the two methods. 



f In these two the sectors were supposed to be set at 135 and 80 respectively, 

 but after the set had been taken and the sectors stopped it was found they read as 

 in the table. 



u 2 



