342 On the Heat engendered by the Fall of a Meteor into the Sun. 
of rays in passing through the atmosphere. It will be remarked 
that T° is the difference of reading between thermometers in the 
sun and in the shade taken with due precautions. 
Some years ago, when in India, I tried this by enclosing a 
thermometer within three concentric boxes well protected from 
external influences, and capable of being equally heated all round 
to any temperature below 400°, by means of flues ascending 
from an Argand lamp. The sun’s rays, when near the meridian 
(having an altitude of about 70° and with the atmosphere per- 
fectly clear and calm), were admitted to fall, when required, on 
the bulb of the thermometer through a narrow triplet glass par- 
tition. I found that 50° was the rise that took place in conse- 
quence of exposure. There being glass partitions on both sides, 
the reading of the thermometer was very distinct by transmitted 
light. Beginning at 80°, without applying the lamp, the ad- 
mission of the sun’s rays caused the mercury to rise to 130°, 
where it remained steady. The lamp was then applied at low 
power, so as to maintain the inner box at this temperature while 
the sun was excluded. When perfectly steady, the sun’s rays 
were readmitted, and the mercury again mounted with the same 
alacrity as before, until it reached 180°. This continued step 
by step up to 250°. No difference, either in the magnitude of 
the step or the time taken to effect it, could be detected. 
Thus, for 7° we have the constant 50°, and we obtain by 
comparing the disc of the sun with the surface of the sphere, 
At the earth’s mean distance the sun’s diameter is 32’ 3/6, 
hence n= 183960 and «=918000°. 
If there is no fault in this mode of proceeding, we may with 
confidence estimate the solar temperature to be above 10,000,000 
degrees, probably 12,000,000, allowing a reduction of one-third 
from absorption in passing through the atmosphere and the 
three plates of glass. 
A notable fact, in making these observations, is that the step 
7° seems wholly independent of the temperature of the medium 
in which the thermometer lies. Why this should be, is apparent 
from the equation. Substituting 2¢ for ¢, and consequently 
2—t in place of x, is tantamount to heating the box from 80° 
up to 620°. Let 7’ represent (in degrees) the step at this higher 
temperature 2¢, we have 
2t-+a—t+(n—1)2¢ 
n 
u J 
=2t+7' and e—t=nr7' and = = wide. 
Thus the step diminishes only about the zs4)sth part, or 4pth 
of a degree during a change of upwards of 500° in the box. 
From Mr. Carrington’s observations it appears that the burst 
of light was of much greater intensity than the sun’s normal 
