1891-92.] 
Meetings of the Society. 
273 
screws ; and so successfully was this principle carried out, that in the 
final apparatus the angular motion registered on the recording paper 
was 16,800 as large as the motion of the grating by which successive 
lines of the spectrum were brought into view, while the computed 
probable error in the registration was only about three-fourths of a 
second of arc. 
The observations were made at a station set up by Lord Crawford 
on the Barmekin Hill on his property 850 feet in height. On this 
hill Dr Becker camped out during the summer months of 1887, 1888, 
1889. The observations include 32 sunrises, 47 sunsets, and 18,000 
observations of lines, which were made in 45 hours, and 8000 high 
sun observations. 
The reductions of these observations, in the opinion of competent 
judges, have been made with the care and skill which we should 
expect from so proficient an observer. The theoretical reductions 
have been made by tables computed for the purpose, and the 
irregularities noted by the graphical process. In these reductions 
Eowland’s standard lines were used. 
It would be out of place on this occasion to enter into further 
detail; but I may mention that within the region 6024-4861, 3637 
lines were recorded, whereof 928 were shown to be of telluric 
origin. 
Work of the same kind was done by Thollon at the same time 
that Dr Becker was carrying on his observations, and I understand 
that his published results give only about two-thirds of the number 
of lines which Dr Becker has been able to record ; and there is every 
reason to believe that the work of both is of the highest attainable 
degree of accuracy. 
It seems unlikely that further detail can be found unless the Row- 
land grating be superseded by more perfect apparatus, though that 
seems hardly possible. What is most to be desired is, that the 
spectra of the elements believed to exist in the sun should be exa- 
mined with the like powerful instruments and equal skill, in order 
that all the lines of the visible spectrum may eventually be referred 
to their proper constituent elements. 
The following Communications were read : — 
1. Further Remarks on Nova Aurigae. By the Astronomer-Royal 
FOR Scotland. 
2. List of the Fossil Selachii of Fife and the Lothians. By Dr R. H. 
Traquair, F.R.S. 
VOL. XIX. 21/3/93 
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