108 



Mr. Samuel Hunter, 



Fig. 9. 



A curve produced from a similarly constructed machine set at 

 random is given in fig. 10. 



Fig 10 



It is unnecessary to speak of Foucault's process of hand abrad- 

 ing or the American system of local polishers, as these require 

 highly skilled artificers to be successfully used. 



The choice of machines evidently lies between that of Lord 

 Rosse's and that of Mr. Grubb's No. 2. The latter is so compact 

 and admits of such a variety in the curves which the polisher 



