87 
Tt was not, however, till the beginning of 1848, a year and 
a half after observations with the Prime-Vertical Instrument 
had been commenced, that he was officially assigned to its 
charge. The attainment of some definite result concerning 
the long mooted annual parallax of a Lyre, which passes 
within 15’ of the zenith of Washington, was an especially 
cherished problem. For many years he labored towards 
its solution, in spite of serious and most vexatious obstacles. 
But the maxima and minima of the annual parallax occur 
at seasons very unfavorable to observations in the climate 
and atmosphere of Washington; and it was chiefly due to 
this fact, that some result was not long since attained. At 
the regeneration of the Observatory in 1861, he was again 
full of hopefulness and confidence of an early solution of 
this favorite problem, as well as sundry others. “ Your 
rejoicing,” he wrote, “cannot exceed mine; for it is a con- 
stant gratification to see order quenching chaos, energy 
overriding the old slowness, and above all our own science 
raising her triumphant head, and banishing the old hum- 
bug.” Even at that period of his domestic bereavement 
and loneliness, it needed ‘only the unwonted consciousness 
that Astronomy might be protected at the only national 
Observatory in the land, to reanimate his spirits, and give 
im a new stimulus to exertion. The Prime-Vertical In- 
strument, like the others, was soon put into complete order, 
and the traces of early misuse thoroughly removed; and in 
March, 1862, he began a new series of observations of 
a lyre. During the period of this series HUBBARD com- 
pleted an exhaustive discussion of the influence of irregu- 
larity of pivots upon the level-reading at different altitudes ; 
—a determination of the effect and amount of flexure by 
comparisons of the error of collimation deduced from re- 
versing the telescope on a star with that resulting from 
