64 Remarks on Mr Daniel? s Hypothesis . 
December 1821, and from the beginning of May 1822 to the 
end of August of the same year. They were made by means 
of a register-thermometer of large range, having its bulb covered 
with black wool, and placed upon a south border of garden- 
mould, with a full exposure to the sun. The thermometer did 
not rest on the earth, but was supported about an inch above it. 
The maximum-heat of the sun’s rays during the day was thus 
measured, and recorded in the journal.” 
At the request of Mr Daniell, Captain Sabine made many 
observations for the same purpose, in different places within the 
Tropics. From a comparison of the results obtained by himself, 
with those of Captain Sabine, he infers, that the intensity of the 
sun’s direct rays decreases as we approach the Equator. And 
extending the comparison to a few facts connected with this sub- 
ject, which are recorded in the late voyages to the Arctic Regions, 
he considers the conclusion to be incontrovertible, That the in- 
tensity increases proportionally as the distance from the Equator. 
A theory is given in support of this singular proposition ; but 
with respect to this, we have no doubt Mr Daniell himself has 
already discovered the oversight by which he has been misled. 
A consideration of the experiments themselves will, however, 
afford some interest. But it must be here observed, that Mr 
Daniell, in his Essay, applies the term, “ force of radiation,” in- 
discriminately to phenomena essentially distinct; so that the ac- 
tual power of the sun’s rays is confounded with the excess of 
temperature indicated by a thermometer exposed to the sun, 
above the temperature of the air. As it is only to the former 
that my remarks are at present directed, instead of the table 
given in the essay itself, we shall extract from his journal the 
maximum temperatures registered by the black thermometer. 
January, 
60° 
May, 
135° 
September, 
120° 
February, 
80 
June, 
154 
October, 
104 
March, 
97 
July, 
128 
November, 
72 
April, 
110 
August, 
144 
December, 
66 
Here the 
maximum 
observed 
is 154°. 
This took place on the 
5th of June; on which day, the little breeze then blowing being 
from the north, the thermometer must have been completely 
screened from its cooling effects. Of the tropical observations, we 
shall quote only those made at Bahia and Jamaica, as they alone 
