tf an Arc of the Meridian . 
4 % 
Table for supplying the necessary Correction to the observed Zenith 
Distance of a Star, on account of the Expansion or Contraction 
of the sectorial Tube by i° of Heat. 
Zenith 
Correction 
Zenith 
Correction 
distance 
for 
distance 
for 
observed 
i° of heat. 
observed. 
i* of heat. 
• 1 
„ 
O 9 
IT 
1 
0,Ol8 
4 30 — 
0,084 
1 30 — 
0,028 
5 — 
0^93 
2 — * 
o.o 37 
5 3 ° — 
0,102 
2 30 — 
0,04b 
6 — 
0,11 1 
3 “ 
0,056 
630 — 
0,121 
330 — 
0,065 
7 — 
0,130 
4 “ 
0,074 
73 0 — 
0,129 
In using the above Table, the corrections are to be taken as 
negative, if the upper thermometer denotes the air to be hotter 
towards the top of the observatory than round the limb of the 
sector; and positive, if the reverse. 
3 p * 
MDCCCIII. 
