[ ol J 
XII. On the Temperature of a Room indicated by two Thermo- 
meters at different Altitudes. By Jonn Murray, F.L.S. 
M.W.S. &c. Se. 
To Dr. Tilloch. 
Sir, — Ox my return from the Continent in 1819, I brought 
with me Breguet’s * Thermometre Métaluique,” —an instrument 
susceptible of the most delicate sensibility, aud with which J have 
made many interesting experiments. In a still room without a 
fire, in the summer months, it readily communicated the differ- 
ebce in temperature between the floor and a chair, and this last 
and the table. 
The phenomena induced me to make a series of experiments 
on the difference of temperature indicated by two thermometers 
at different altitudes, yet otherwise under similar circumstances. 
In the first series of experiments made at Nottingham from the 
21st to the 28th October last inclusive, 1 was surprised to find, 
that any deviation from its uniformity had an immediate relation 
to the radiation of the terrestrial temperature to the heavens ;— 
indeed, I am much deceived if the difference in question may not 
be found as accurate a guide as the barometer itself. Since I 
came to London, I have kept a pretty accurate register of the 
difference between two thermometers: one placed with its bulb 
on the floor, and the other suspended 63 feet above it, embracing 
the period betweeen 5th and 24th November, On the IlthI 
began first to note the phenomena of the weather in correspon- 
dence with these changes, and it will be there seen, that when the 
difference exceeds 2° to 2°5 F. the weather has been variable 
and wet. The following comprise the results of the observations 
in a tabular form. 
The following experiments were made at Nottingham with 
thin calico curtains to the windows of my room. 
Date of pour Pos, ot} Temp. |Dif. be- 
Obser. opr, Therm.| indicated. | tween 
Ts21. | ua. Mm. 4 
Oct 21) 9 30 a.m.|Floor | 56°5 F. 
wy ER 
6ytect| 575 | $|) F- 
9 30 v.m.!Floor | 58 Ul a5 
63 feet | 59°5 ) 
24| 7 30 pe. .|Floor | 59 tly 
64 feet | 61 5 
25) 2 p. m.\Floor | 59 lo 
\64 feet | 61 5 
8 p. M.|Floor | 60°5 iiss 
64 feet | G4 Wie 
26)10 30 »..|Floor | 63 a| 25 
64 feet | 66 i Pi 
28) 9 p.M.|Floor | 70:5 Ye 
1G) feet |° 72°7 § 
ee mm acenmmmmnn eemenaenits 
