Remarks on Mr DanielVs Hypothesis. 63 
It will be seen, that, throughout these experiments, the egg 
maintained a temperature superior to that of the external me- 
dium, even, in the latter instances, though that medium was 
considerably exalted. 
mil Nov. 1825. 
Art. XI.- — Remarks on Mr DanielVs Hypothesis of the Ra- 
diation of Heat in the Atmosphere. By Mr Foggo junior. 
Communicated by the Author. 
The few remarks I am to offer on this hypothesis, were ori- 
ginally intended to have been inserted in a note to the Meteoro- 
logical Register published in this Journal. It has been thought 
proper to give them a separate place, chiefly with the view of 
exciting more attention to the subject among those who have op- 
portunities of prosecuting such inquiries. 
Before the publication of Mr Danielfs essays, solar radiation 
had never been treated of to any extent more than conjecture, 
or a few unconnected experiments. Besides the interest which 
it possesses as a subject of experimental research, there are seve- 
ral questions of the highest consequence to physiology, which 
depend upon our knowledge of this important agent. Some of 
these, which Mr Daniell himself had principally in view, are 
here given in his own words : 64 Does its influence increase with 
the temperature of the air from the Poles to the Equator ? ” or, 
44 Is the rapid vegetation of the Arctic Regions, during the short 
summer of these climates, dependent on any compensating ener- 
gy of its operation ? Before I attempt to answer these ques- 
tions, I shall propose another, which many will be surprised to 
find cannot be met with an immediate solution ; which is, the 
maximum degree of heat to which a plant, or the parts of a 
plant, are subjected, by exposure to a mid-day sun, in mid- 
summer, in this climate ? There are, no doubt, in all plants, 
parts which are calculated to absorb all the radiant heat which 
strikes upon them ; and it is therefore desirable to know, with a 
reference to this subject alone, the utmost amount of tempera- 
ture which radiant matter is capable of producing. My Mete- 
orological Register includes a column for observations upon this 
point. They are complete from November 1820 to the end of 
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