Avrnnty—Photographs of Spark Spectra from the Rowland Spectrometer. 337 
spectra are in preparation, but it has been thought inadvisable to delay the pub- 
lication of reproductions of the spectra until the measurements are completed, 
both on account of the differences in number and character of the lines above 
referred to, and also on account of the very clear way in which the characters of 
the spectra and of their component lines are shown therein. 
Scales of wave-lengths, based upon Kayser and Runge’s measurements of the 
iron lines, have been ruled on the original photographs, by means of which the 
lines in the spectra may easily be identified, or otherwise, with measurements 
which have already been published in various tables of wave-lengths. 
Hach scale division is equal to five units on Rowland’s scale ; the division of all 
the scales are very nearly of equal magnitude in linear measurement. They have 
been ruled in two portions corresponding to the two sections in which the spectra 
had been photographed. The division on the less refrangible sections are each 
approximately equal to -0944 inch, and those on the more refrangible sections to 
0943 inch. 
A vernier has been ruled for each section, by means of which the wave-lengths 
of the lines may be approximately read off to 0°25 of a unit. 
The errors of the scales of each spectrum are approximately given in the 
following table :— 
Less REFRANGIBLE SECTION. 
WAVE-LENGTHS. 
SPECTRA. | 
4500 to 4300 | 4300 to 4100 | 4100 to 3900 | 3900 to 3700 | 3700 to 3500 | 3500 to 3300 | 
Ru, Mn(Pt&K), . . 0-00 — 0-05 010 | =OnG — 0:20 ~ 0-25 
Ni& Au, . 
Fe, Rh, Pa, Os, In, + 0°15 +010 +005 + 0:00 — 0:05 ~ 0-10 
Pt, Or (Pt&K), . .| +0°30 + 0°25 +020 | 40-15 + 0-10 + 0:05 
Gyo « co o of 0x + 0-40 40°35 | +030 | 40-95 +020 | 
More ReEFRANGIBLE SECTION, 
WAVE-LENGTHS. 
SPECTRA. Sn el 
3400 to 3200 | 3200 to 3000 | 3000 to 2800 | 2800 to 2600 | 2600 to 2400 | 2400 to 2200 | 
Pd, Cr (Pt&K), Au,. 0-0 = 0-1 — 0-2 — 0:3 04 | =O 
Fe, Bh, Pt, Mn (Pt & K),.| + 0°2 +01 0-0 ~ 0-1 ~ 0:2 — 0:3 
Oster | eee ees) 059 ~ 0:3 ~ 0-4 ~0°5 — 0:6 0-7 
Come. MEMES eee 0:3 — 0-4 ~ 05 — 0-6 — 0-7 — 08 
Trquede sy 5 eee Mae | B= 10:5 ~ 0-6 0-7 ~ 0:8 ~ 0:9 ~ 1:0 
RAGE. .o o | Ox -- 08 — 0-9 ~1:0 = il -12 
