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LXIX. 
ON THE MOUNTING OF THE LARGE ROWLAND SPECTRO- 
METER IN THE ROYAL UNIVERSITY OF IRELAND. By 
W. E. ADENEY, D.Sc., F.LC., Curator in the Royal Univer- 
sity, anv JAMES CARSON, A.R.C.Sc.1., C.E. 
[Read Fesruary 16; Received for publication Frsruary 18 ; 
Published Aprin 7, 1898.] 
Tue working parts of this instrument were obtained from Mr. 
J. A. Brashear, of Allegheny, United States of America. They 
consist of two interchangeable inverted | steel rails, each of about 
23 feet in length, and each haying the upper edge planed to an 
inverted (\ section, with top truncated. 
These rails were supplied with saddles of cast iron, into which 
the rail was fixed, and which were provided with levelling and 
lateral adjustment screws. 
One of these saddles takes one end of each rail at right angles, 
one to the other, and also carries the mounting for the slit. 
The ‘‘diagonal beam” is an iron girder consisting of a tube 
about 3” diameter (t, fig. 1), trussed with 2” rods (r, fig. 1), the 
struts being placed at angles of 120° round the tube. Fixed to 
each end of the tube is a cast-iron palm (g, fig. 1), which is provided 
with a small range of adjustment in the direction of the length of 
the girder. 
These palms are provided with vertical axes, which form the 
connexion with the carriages (1, fig. 1), which run on the rails. 
On the one palm is fixed the grating holder (a, fig. 1), and on 
the other the camera. These parts are similar in structure to 
those described and illustrated by Ames in the Astro-Physical 
Journal, p. 28, January, 1892. 
The concave grating, which was also obtained through Mr. 
SCIEN. PROC. R.D.S., VOL. VIII., PART VI. 3G 
