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echelon spectroscope concerning the difference in wave-length between 
the components of the outer components of the sextet of the blue 
(4358) line of mercury. The following table is an extract (OA; in A.U.) 
H Dd, 
CU JS i EEE PE: 
Lo UA) A AN te ee eS eg 
12.900 0.052 
20.000 0.098? 
21.300 0.09 
23.400 0.098 
For a value of the field between 12.100 and 12.900 the splitting 
up of the lines becomes sufficient to make them appear as separate 
lines on a photograph (upon which the measurements were taken). 
Two lines can of course be seen separated at a considerably smaller 
distance. 
0,052 
4358 
For the echelons of these observers we have t= 7,5, n= 15. 
With these data I calculate g; = 5,3.10—°. 
Thus it appears from the data given in this paper that it is 
possible to manufacture echelons, performing nearly as well as they 
are theoretically capable. 
Thus now q= = 11,9.10-# and ge considerably smaller. 
Mathematics. — ‘Considerations in reference to a configuration 
of SearE”’. By Prof. P. H. Scnoure. (Second part). 
5. We have already remarked that the form of the equations 
of the fifteen lines obtained in the first part of this communication 
was not yet a quite regular one. If we shorten 7; — #3 = 2; into 
(1 — 8), 7;= 27, into 12 and if everywhere we omit the equations 
a) = 0, 19 = 0,...2%,=0, then the following table gives the obtained 
result in the form of the determinant repeatedly used 
