: 

Some Spectroscopt e Notes. 457 
Our own measurements represent the line as sixfold 
when most highly developed, the distances of the satellites 
being —0°208, —-096, —°059, 
Fig. 5. +0°032, and +0°067, with 
the condition that these figures 
A are right .only to a niult iple 
of -464 the distance between 
| a two successive orders. When 
a faint line is seen in the 
me-eOn + 059 *032 field — the echelon spectro- 
“096 -067 = scope was the instrument with 
which our observations were 
made—the different orders of the central line D are very 
close together, and it is impossible to tell to what order the 
faint line belongs. Considerations of symmetry lead us to 
suppose that B GE and F are rightly placed. It is quite as 
probable that A is on the other ‘side of D at a distance of 
+°256.  - 
These measurements were made on an ordinary Geissler 
tube with aluminium electrodes, and were verified on a tube 
the electrodes of which were little mercury cups. The tubes 
were fed from an induction-coil that gave a 10-inch spark. 
The E.M.¥. in the primary was usually 6 volts. 
The system did not always appear as above. B and C 
appeared at times as one, as so also did HE and F. In that 
case the distance of (BC) was *084, and of (EF) -069. 
Then BC might be a doublet and EI’ a single line, or the 
system might reduce to two satellites corresponding to A and 
the unresolved doublet BC. It was usually thus when a less 
powerful induction-coil was used. 
Although Zeeman did not measure the position of the 
satellites with his echelon (which is slightly less powerful 
than ours), he apparently obtained the same arrangement, for 
he says, in the article quoted above: “ Using the echelon in 
a position in which two strong lines of equal intensity cor- 
responding to successive orders of the radiation were v isible, 
I could distinguish also five faint, very narrow lines between 
the principal ones. The distance between two pairs of these 
lines was very small.” 
The doublets (BC) and (EF) at. times appeared as single 
lines. The single line was not the doublet badly defined ; 
its width was not greater than that of one of the components 
of the doublet. Capacity and inductance in the primary and 
secondary had no effect on the satellites. They were usuaily 
seen best when the hammer of the induction-coil was going 
jerkily—when it was screwed up, so that its spring was 
short. 


