37 
concentric adjustment of a triple object-glass. 
equal stars as those of 44 Bootis and <r Coronas, or of ex- 
hibiting the minute secondaries of j3 Orionis and 24 Aquilas, 
with as much distinctness as the state of the air will admit. 
The actual limit to its powers cannot be fully ascertained, 
excepting under such favourable conditions of the atmosphere 
as do but rarely occur. 
