180 € G. Rockwood—Motion of a Tower by Solar Heat. 
incorporate them in this discussion. 
The recorded observations give a series of level-readings at 
certain hours upon 59 days. e most obvious method of 
any one day. Thus combined, the means are as follows, the 
levels being designated by the numerals I and II, and the level 
readings having been reduced to seconds. 
Mean Level Readings. 
+East. 48 
rT -8""6§ 095 = 157 — 762 10/87 = — 10 
+North. 1136 
IL +5/"64 +5/1-03 +2/'-97 —0/-37 — 0/78 +S 
If now we let these numbers be the abscissas and ordinates 
of a plane curve, referred to rectangular axes in the direction 
the normal to the plane of the levels or by om vertical line gs 
the tower. It should also be borne in mind that a south lev : 
reading indicates a north inclination of the tower, and vice versa, 
1, 2, 3, ete., in order, beginning with the ere 
ing observation. It is seen to be an imperfect fen with 
i an 
7 
minor axis coincides nearly with the meridian. It thus pe 
sponds tolerabl 
minor axis of the 
ing has checked the north and south motion, and so 
