-- § Ona New Method of recording differences of Declination. 
ferences of declination) to forty hundredths of one second of are. 
But the old methods have already been pushed to their ultimate — 
limit of attainable precision. Of this, I think any one will be 
convinced who will read M. Struve’s admirable History of the 
Pulkova Observatory and its instruments. On the contrary, in 
‘the new method almost nothing has been done. Any one who 
has used telescopes of low power and those of great power, need — 
not be reminded of the extraordinary advantage which high op: 
tical power and good definition gives in bisecting a star. 4 
n the great refractor of the Cincinnati Observatory, ¢ Bootis — 
is divided into two beautiful stars some two seconds of are asun- 
der, each round and sharp, while in the small instrument used 
in the foregoing observations the same star appears as a single — 
object, a large mass of light. In case it were possible to employ 
fae ortiens power of the great refractor, the most astonishing — 
_ Increase of accuracy might be anticipated. If such an object 
glass were mounted as a transit, the records would then be made. 
+ 
very conveniently on the cireumference of a circle thirty feet in 
power of stereotyping the positions of the instrument, so that the — 
observations may be scrutinized at leisure and be read and re- 
until the error of reading up shall be reduced to an insensible 
quantity ; this cannot be done in any other method. oo 
at then may we not anticipate from the application of this 
new machinery under favorable circumstances to the examination 
of the heavens. If Struve dared pronounce his instrument com — 
petent to the determination of parallax, proper motion, é&c., with — 
results discrepant to two-tenths of one second, then indeed has 
the new machinery converted a small inferior transit into an instr 
ment competent to cope with these grand mechanical | ions. 
