The view of the Potomac and of the hill and buildings of George Town was
very extensive and remarkable; but before we had feasted our eyes
sufficiently on it, we were summoned to see one of the most lovely
sights I ever witnessed. Though it was mid-day, and the sun was shining
most brilliantly, we saw the exquisitely sharp crescent of Venus in the
pale sky, and about half the apparent size of the moon. The object-glass
of the instrument was divided into squares, and she passed rapidly
across the field of the telescope, sailing, as it were, in ether; by the
slightest motion of a tangent-screw of great length, we were able to
bring her back as often as we liked, to the centre of the field. This
mechanical process might, however, have been rendered unnecessary, had
the machinery attached to the instrument been wound up; for when this is
the case, if the telescope is directed to any star or point in the
heavens, it continues to point to it for the whole twenty-four hours in
succession, the machine revolving round in the plane to which it is set.
The instrument is a very powerful one, and, like the smaller one we
looked through before, was made by Fraunhofer, a famous optician at
Munich. There are some other very wonderful instruments which we had not
time to see, as we had to make desperate haste to get some dinner, and
be off by the late train to Baltimore.
Pages:
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139