40 REPORT—1874. 
This is proved by five years’ daily observations at Strathfield Turgiss, Hants, 1869- 
74; two years’ at Hawsker, near Whitby, Yorkshire (1869-71); and one year’s 
observations in 1872, at Harpenden, Herts. 
2. It was also found by the above observations that N. and N.W. winds, which 
contain little moisture, are very favourable to solar radiation, whereas S. and S.F. 
winds are usually accompanied by much less powerful sunshine. The N.E. winds of 
spring, which are excessively dry, are also accompanied by intensely powerful solar 
radiation. 
3. By frequent observations during cloudless weather with nearly constant va- 
pour-tension, curves are obtained representing the daily variations in solar radiation 
produced by the changes in the sun’s altitude and consequent alteration of the 
length of the path which the beams pursue through the atmosphere. From these 
the percentage of the sun’s heat-rays which would be absorbed by the atmosphere 
if the sun were vertical can be approximately determined, assuming that the ten- 
sion of yapour remained as it was on the day or days of observation. It is then 
possible to calculate the amount of radiation due to the altitude of the sun at noon 
in the middle of each month for a constant vapour-tension, and to compare this 
with the amount actually observed in each month on cloudlessdays. In this way itis 
found that when the tension of vapour falls below the amount on the day which 
furnishes the data for calculation, the radiation rises above the calculated amount, 
and vice versd. In fact the sun’s rays are more intense in winter than in summer, 
when the difference of altitude at noon is allowed for, because the absolute amount 
of vapour in winter is so much less. About ten or twelve per cent. is the mini- 
mum of absorption of the sun’s heat-rays, while the maximum equals or even 
exceeds 20 per cent. 
The paper concludes with a few observations on the increase of solar radiation 
with elevation above the sea-level, from which it would appear to have amounted, 
between the heights of 470 to 1800 feet, to about 5 per cent. of the amount observed 
at the lower station when the sun’s altitude was 20°, and to above 3 per cent. when 
the altitude was 26°. 
On the Necessity for placing Physical Meteorology on a Rational Basis*. 
By Lieut.-Col. A. Srraner, F.R.S. 
The author points out the two great branches into which the science of mete- 
orology is divisible, viz. that which is concerned with its great fundamental laws, 
and that which concerns climate—the first being of a cosmical, the second of a more 
local character. The present paper refers principally to the first of these branches, 
which he considers to have been greatly neglected, and to need being treated on 
systematic and rational principles. 
He indicates the elementary considerations which point to the sun as the chief 
origin of meteorological phenomena, and recommends, now that science has pro- 
vided many of the necessary means for the purpose, that the physical study of the 
great central luminary should be commenced in earnest. 
He points out that such solar researches as have been undertaken, though most 
valuable as far as they go, are insufficient because their continuity is interrupted 
by cloudy weather. He holds that we require a daily record of the changes which 
are perpetually going on in the sun, in order to trace their course, their character, 
and their laws. He points out that this indispensable object can only be attained 
by establishing a certain number of stations, equipped for such rssearches, so 
situated that there shall be a fair probability of clear weather daily at one or more 
of them. He mentions India as peculiarly suited for the purpose on account of 
the great variety of climate to be found there. 
He maintains that such investigations must devolve on the State, and lays down 
the broad principles applicable to the particular case in question. The first prin- 
ciple is that private enterprise should, in all matters within its scope, be encouraged 
and aided in every possible way. The second principle is that the State should 
step in where private enterprise fails, and itself conduct scientific research, whether 
obseryatorial or experimental, subject to the following main conditions ;— 
* Published in ‘Nature,’ vol. x. p. 490 (Oct. 15, 1874). 
