282 PROFESSOR L. BECKER ON 
Taste XITI.—TZable of a, of Corresponding Points of Four TaBLrE XIV.— 
Bands and of the Intensities, showing that the Bands are Structure of 
semilar mn regard to their Wee: Lengths after August 1, the Bands after 
1901. August 1901. 
a@ in Tenth-metres. Degrees of Intensity. 
as Mean 
Adopted 
No. Am Am am Degrees 
of 
T. M. Intensity. 
3869°4 | 3968°0 | 4364°4 | 4726-3 |3869°4 |3968:0 | 4364°4 | 4726°3 
1 — 18°5 3 — 18:9 9 
2 — 15°6 — 15°55 — 15:3 15°3 —15°4 
Sol Say) Faso Sasa | st cane ems re) _ 13-3 3 
: : 7 4 (12) (11) ; 9 
4 — 116 —11°9 — 11°5 
5 TH) Cel ES ef rea ' ll 
5 —- 96 — 9°8 9°3 8 7 7 (11 — 94 9 
Gy ayo Plo ge | Seon aaa ) _~ 78 
il 2 ih ol Or0) ] 
if - 65 3 3 1 7 — 6°5 9 
Gu et glee ere) een z CD) = BO z 
$s EAE he Bilpeal() 10 10 10 
9 = 7 = 17 => =1h9] lis 6 A 5 7 —- 14 5 
10 + 16) + 1:5 + 09 + 07 10 9 10 9 + 1:2 10 
1l + 4:1 + 3°6 9 9 8 9 + 38 9 
1 + 5:5 + 56 + 5:6 + 51 5 3 3 9 + 5:4 3 
1133 + 83 + 73 + 76 + 87 5 2 + 80 
10 8 55 8 
14 4 | elo 4107 
+11:0 +11:9 ; te we 5 a: 5 
15 +11°6 8 6 7 5-5 +11:9 s 
16] +140] +144) +144] 4133] 3 5 3 > +140 
17 +15°8 + 16:2 ne + 15:5 1 1 (3) 1 +15'8 1 
18 + 22°8 + 20 +18:1 + 20:0 i + 20°2 
02 t.m. for a@,, and 0°2 t.m. for d,,. The observed degrees of intensity also agree 
satisfactorily with the calculated ones, or their sums at those places where two or three 
bands are superposed. The average difference, apart from signs, is 0°7 degrees of 
intensity ; 91 of the discrepancies lie between 0 and 0°5, 60 between 0°5 and 1, 26 
between 1, and 2 and 6 are greater. I consider it therefore proved that the bands are 
in every way defined by A,,, the degree of intensity of their maximum, and the 
quantities given in Table XIV. 
13. Permanency of Structure.—Table XV. gives the number of observations of a 
minimum, and the period during which it was observed. The bands 2,,=3869 and 
3968 were outside the range of the photo-plates Nos. 8 to 17. Their position is never- 
theless well determined, since the plates Nos. 18 and 19 contain all the six minima, and 
Nos. 20 and 21 each four. The first minimum appears to have been the most pro- 
nounced, In all, it was recognised 90 times, against 47 for the second minimum and 
38 for the third minimum. Of the total of 177 minima, 158 belong to the 1901 plates. 
The number of the minima that have been found seems to depend on the brightness of 
the bands, and still more on the linear width of the minimum, which at wave-length 
3870 was 0°23 mm., and at 5006 only 0°08 mm. In conformity with this, the 
