of the Spectral lines of the Elements. 215 
red to lines upon Kirchhoff’s scale, Mr. Airy, in his interpola- 
tion, employed only six, the intervals between these amountin 
respectively to 101°4, 308-7, 520-9, 556°3, 774-7, scale divisions, 
Through these six points Mr. Airy endeavors to draw a para- 
bola of the 5th order. He then employs the 101 other lines 
measured by Ditscheiner only to compare with the numerical 
results given by his single formula. 
As Mr. Airy has quietly ignored the existence of my reduction 
of Kirchhoff’s scale read before the National Academy of Sci- 
ences in August, 1866, and published in abstract in this Jour- 
nal for January, 1867, I naturally inferred that his work would 
prove so much more perfect than my own as wholly and justly 
to supersede it. The following comparative tables of differences 
will show, I think, that this is not the case. For the sake of 
completeness I add a column of differences obtained in m 
second reduction of Kirchhoff’s scale, in which Cauchy’s 
method of interpolation was used, and weights were given to 
e observations 
Taste XII, 
y. Gibbs 1, Gibbs 2 A Gibbs 1. 
+0°25 +6°08 —0:06 +201 +0°01 —0°05 
+043 + 0°24 +0°02 41°87 071 —0 23 
+ 0°69 —0°02 +0°08 42°12 +0°02 0-01 
+0°90 —0'08 +008 42°32 40°07 +012 
0 —0'15 42°18 —O1l —0-0 
+103 +0°06 0-00 42°21 +0711 +001 
+1°02 0°02 —0:04 +204 +0°04 +008 
+115 —0°06 0-00 1°82 0-1 00 
+1:22 —0-0 + 0°05 +162 + 0°04 
+131 +004 ‘00 +100 —0'5 —O'15 
+1°38 +0°09 —0:06 +1:10 +004 +0°07 
+ 0°58 —0-26 —0-02 +0°67 +0°04 +0-09 
0 +0°05 —0°05 +0°34 + 0°02 0 
+001 +0°10 —0°02 +0°27 +0°08 —0 03 
+0°44 +0°09 +0°35 00 +006 +0°06 
+100 —0°0 —013 —0'53 +0°05 +0°32 
+104 a) —0'18 —1°39 40°01 —0-16 
+125 +020 + 0-06 1:90 —0°04 +023 
+1°23 +017 +0°02 —2°46 0:00 00 
+1°26 +0°06 +009 —2°60 —0-19 
+129 +0°15 +0-07 3°52 +049 —0-18 
+111 0-0 —0°08 —3°57 +012 +009 
+122 +010 00 —401 —0-03 0-22 
+0°32 0-00 4°32 —0°01 +0°30 
+1-23 +0°03 0 00 —551 —0:26 —0% 
+1-09 —00 —0-06 —5-32 —0°08 + 0°05 
+166 +0°25 0°59 ~6°43 —0°-20 —0-02 
+153 +009 +0°26 6-83 +0°01 1-06 
+0:97 —0°05 =—007 —7'59 _ +0°34 
+0°93 +0-05 +0°02 —8-23 0-10 +018 
+0°90 +0°09 +004 es —0'14 _ 
+0°72 +010 —0-07 +0°38 —0°66 
07 0-00 +004 
+056 +002 +0: —9-30 + —O17 
