i66 



RADIOMETRY. 



Table VII. Bolometer-Galvanometer Sensitiveness. 



Observer. 



Langley ( AnnalsAstrohpys 

 Obs.) 



Abbot (Astrophys. J., 18, 

 p. i; 1903) 



Angstrom: 



Wied. Ann., 26, p. 



253'. l88 5 



Wied. Ann. 36, p. 



715; i889 



Wied. Ann., 48, p. 



497; 1893 



Julius (Licht und Warme- 

 strahlung, p. 31; 

 1890) 



Helmholtz (Verh. Phys. 

 Gesellsch., Berlin, 

 7, p. 71; 1888).... 



Lummer and Kurlbaum: 



Zs. fur Instrumenten- 



kunde, 12, p. 81; 



1892 



Wied. Ann., 46, p. 

 204; 1892 



Rubens: Wied. Ann., 37, p. 



255; l8 89 



Wied. Ann., 45, p. 

 238; 1892 



Galvanometer. 



Resist- 

 ance. 



ohms. 



[.6 



2.7 



5 

 80 



Full 

 period. 



Current 



sensitiveness 



for 1 mm. 



deflection. 



Bolometer. 



20 



l6 



4 to 5 



1 to 5X10- 10 



5Xio- 



5.7X10- 9 

 4Xio- 



8X10- 9 



1. 5X10- 



3.2X10- 10 

 3.2X10-1 



Resist- 

 ance. 



ohms. 

 4 



8.8 



60 



5-2 

 3 



Area. 



sq. mm. 



0.05 to 0.02 

 Xl2 



O.1X12 



O.3X14 



12X1X32 



7X0.3X3S 

 3X0.2X10 



Bolometer 

 current. 



amp. 

 O.03 



O.I33 



0.006 



0.2 



