456 Description of the Great Southern Telescope.  [Oct., 
Fra. 10. flexible hoop, as in Fig. 10, to 
preserve them from strain, 
and consequently it was im- 
CG Q) possible to mount them 
equatorially, when they would 
sometimes be turned upside 
down and would roll out of 
their hoop. Mr. Lassel in- 
geniously got over this diffi- 
culty by making his telescope 
revolve in its cradle so that 
he could always keep one 
diameter vertical; but this 
plan, apart from its inconve- 
nienceand clumsiness, destroys 
all accuracy of adjustment. 
Mr. Grubb’s system will be best understood by reference to 
Figs. 11 and 12. Both these figures are sections of the speculum 
Fie. 11. 
Speculum. 
A B 
Oo 
and its box, Fig. 12 being enlarged to show better the rings of 
support. C is a portion of the speculum-box, to which is attached 
on the inside a wrought-iron ring of the section shown at A; this 
may be considered inflexible from its construction. On this rmg 
hangs another, B, another portion of which embraces the speculum 
round a part that was carefully turned by revolving grinders. 
Now this rmg B may be considered as the indispensable flexible 
