194 W. Gibbs on the wave lengths 
Art. XV.—On the wave lengths of the Spectral Lines of ‘the 
Elements ; by Wotcorr Gress, M.D., Rumford Professor in 
Harvard University. Read before the National Academy of 
Sciences, Aug. 16, 1867. 
In 
1864, M 
positions of a number of spectral lines. The scale selected 
accuracy it seemed to be desirable to extract from them all the 
information which they were capable of giving. For this pu 
ose I have endeavored to determine the wave length of 
ne with as much precision as the present state of science pe 
mits, and in this manner to form tables which might enable 
me to determine whether the spectral lines are distributed alc 
cording to definite laws, and if so, whether they can be consid- 
ered as particular cases of the general principle of interfer 
ences, 
° 
fied with particular elements and expressed in ten-millionths 
of a Paris inch. These were reduced to millionths of a milli 
Oxygen 32 Thallium 16 Mercury a4 
Hydrogen 1 Silver 18 Cobalt bee 
Nitrogen 74 Tellurium 44 Arsenic 31 
lum 9 Tin 18 ea 
Potassium 15 Tron 102 8 
ium 3 Cadmium 15 Chromium 64 
Calcium —_50 Antimony 67 smiu 18 
x 1 Gold Palladium 
Strontium 71 Bismuth 44 Platinum =? 
Manganese 46 
that I have reduced them in m 
of a normal map of the solar Spectrum.* Thatis, I have take 
ngth of the more refrangible line of D, as ee | 
trom, instead of 588-8, which 18" | 
* This Journal, II, yol. xiii, p. 1, Jan., 1867. ft 
