THE 
SCIENTIFIC PROCHKEDINGS 
OF THE 
ROYAL DUBLIN SOCIETY. 
ON GREAT TELESCOPES OF THE FUTURE. 
BY 
HOWARD GRUBB, F.pr.A.s., 
Honorary Master of Engineering, University of Dublin, 
Abstract. 
[The full Paper read February 19th, 1877. ] 
IN this paper the author discusses at length the advantages and 
disadvantages of the various forms of telescopes; how and to 
what extent these advantages and disadvantages would be 
modified by any great advance in size over these telescopes at 
present in existence; the practical difficulties of construction of 
said instruments, and the most promising manner of overcoming 
these difficulties. 
In discussing the advantages of the refractor over the reflector 
the author shows, as regards the greater brilliancy per unit of 
surface of the refractor that this advantage lessens by increase of 
size, and that a size must shortly be reached in which this 
advantage will vanish altogether; while as regards the greater 
permanence of collimation, preservation of optical parts in 
good working order, and general suitability for ordinary observ- 
ing work, the author shows that monster telescopes of the future, 
when erected, willin all probability be devoted to special work 
which could not be done with smaller instruments; and that most 
of these advantages diminish in value with increase of size of 
instrument, whereas some of the advantages claimed for reflectors 
VOL, I.— PART I, B 
