178 =. G. Rockwood— Motion of a Tower by Solar Heat. 
The tower is connected by its north side with the main build- 
ing for an altitude of about 45 feet. Projecting from the south 
side of the main building, it has its north wall in a line with, 
and forming part of, the south wall ef the building. The whole 
edifice stands in a position inclined to the meridian, the sides 
of the building, and consequently those of the tower, having 
the direction N. 28° 30’ E. ‘ 
revious observations elsewhere (at Bunker Hill Monument) 
had led to the apprehension that such a tower, besides being 
subject to tremors communicated from the ground, would have 
a definite and somewhat regular daily motion, dependent upon 
the influence of the sun’s heat in expanding the materials of 
which it was composed. The object for which this investige- 
tion was undertaken was to ascertain whether this motion 
would affect the use of the telescope or not. 
In order to investigate the motion in the present case, two 
some of the records being afterward rej 
upon 59 days, included between April.24th and Jul 
Tt will be 1 oe i is peri 
