312 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
r’f’p'h was duplicated on the opposite side in r’’f’’p’’. When the 
lateral glowers f’ and f’’ were swung into the center, the three formed 
a compact prismatic combination, which generated the powerful 
illumination necessary for the blue-violet and green. A cross-section 
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Fig. C. Front perspective view of lamp. a, wooden, base; 6, arch of brass; 
c, mercury cup; e, copper plug; f/f, f’, f’, Nernst glowers; Ah, wooden column; m, 
pivoting point; n, screw; p, p’, p’’, posts; r, 7’, r’’, arms; s, adjusting screw. 
of this combination is represented in the plan of the apparatus, Fig. A, 
by the triangle of three dots atl. For yellow only f and f’ were needed, 
while the single, central glower was sufficient for red. In the latter 
two cases the unused glowers were swung out of the field to.avoid 
the disturbing reflections from them. 
