180 Royal Irish Academy. 



an optician ; and this he did at a price one-fifth the amount which had 

 heen demanded by a London optician for a similar speculum. 



"After this great success, he made many telescopes of from six to 

 fifteen inches aperture, all of which were of high excellence. One 

 important element in those telescopes is the plan of supporting the 

 great specula by a system of equilibrated levers so arranged as to pre- 

 ■\'ent any chance of flexure in the surface, and polishing them when so 

 supported. This plan of support, it may be mentioned, he had deyised 

 many years before for a different purpose, and it was adopted by the 

 late Lord Rosse in the construction of his gigantic instruments. 



"Another very remarkable triumph of Mr. Grubb's mechanical 

 skill was the mounting on an equatorial stand the great 13|-inch re- 

 fractor of the Markree Observatory. Some years before, Troughton 

 had entirely failed in so mounting a 12-inch refractor for Sir James 

 South, and Mr. Cooper was naturally doubtful of the possibility of 

 Grubb's success, but at the instance of Dr. Robinson he allowed the 

 trial to be made. 



"It was, however, thought prudent to experiment first on a 

 smaller scale, and Dr. Robinson had Mr. Grubb to mount equatorially 

 the 10-inch Newtonian at the Armagh Observatory (already referred 

 to) on this plan. The trial was completely successful, and gave an 

 opportunity of experimenting on various forms of driving clocks, which 

 resulted in that conical pendulum which bears Grubb's name, and 

 which, as perfected by Mr. Howard Grubb's mode of electrical con- 

 trol, is equal to the highest requirements of spectroscopic Astronomy. 

 Mr. Cooper's great instrument was then at once constructed as Mr. 

 Grubb proposed, and the Markree Catalogue of 14,000 stars is a true 

 witness to its excellence. By a curious chance, Mr. Grubb was after- 

 wards employed to mount the very instrument with which Troughton 

 broke down, and which Sii- James South presented to the Observatory 

 of Trinity College at Dunsink. How well he has succeeded is shown 

 by the valuable work which Dr. Robert Ball and Dr. Briinnow have 

 done with it, and which has been from time to time submitted to this 

 Academy. 



" The establishment founded by Mr. Grubb in this city became, 

 under his direction, an important source of supply of astronomical and 

 other scientific instruments of precision, and when the University of 

 Melbourne decided on the erection in the Observatory of that city of a 



