: 
Sept. 14, 1871] 
Mr. Stevenson 
MALORE 
393 
due to the interference of three storms.” 
gives a number of instances of interfering cyclones which 
confirm this view. The points of zzferference, where two 
cyclones strike and revolve against each other, are best 
marked by a peculiarly and ¢veacherously fine rain. 
It may not inappropriately be added here that the 
cyclone theory, so strikingly illustrated by the hurricanes 
of the West Indies, has been cemonstrated by Dove to 
apply to the typhoons of the Indian Ocean and China 
Seas. And Mr. Thorn has long since shown that the 
theory holds good for the storms of the Indian Ocean, 
scuth of the equator. 

EXHIBITION AT MOSCOW 
ee Society of Arts has been exerting itself to ensure 
that England shall take part in the International 
Exhibition to take place at Moscow next year. Ata re- 
cent meeting of the Council a deputation was received, 
consisting of M. Philip Koroleff, Conseiller d’Etat Actuel, 
Director of the Moscow Agricultural Academy and Pre- 
resident of the Educational Department of the Exhibition, 
MM. Lvoff, Nicholas Saenger, Secretary of the Society of 
Friends of Natural Science, and the Rev. Basil E. 
Popove. 
M. Koroleff stated that on June 11, 1872, the Society of 
Friends of Natural Science, Anthropology, and Ethno- 
graphy, attached to the Imperial University at Moscow, 
proposes, with the permission of his Imperial Majesty, to 
celebrate the 200th anniversary of the birth of Peter the 
Great, falling on that day, by the opening of a Polytechnic 
Exhibition in Moscow. 
This exhibition, which is intended to form the founda- 
tion of a Central Polytechnic Museum in the old capital 
of Russia, and to present, as far as possible, a complete 
view of the present relations of Natural Science and Techni- 
cology to arts and commerce in Russia, as well as of the 
progress made by the Russian nation in applied sciences 
throughout a period of two centuries, since the time of 
Peter the Great, will, in the opinion of Russian naturalists, 
form a most suitable tribute to the genius of this great 
historical character, and communicate a more elevated and 
especially interesting feature to the festival in his honour. 
This exhibition is not, strictly speaking, an international 
one, for, in accordance with its immediate object, it is pro- 
posed to limit the number of nations represented in it. 
The co-operation of German, French, Belgian, and Dutch 
exhibitors is hoped for, but the desired sympathy and aid 
is more particularly requested from England, which has 
attained, in comparison with other nations, such vast and 
unsurpassed results in that particular sphere, comprising 
the applications of science to art and commerce, within 
the limits of which it is proposed to keep the exhibition. 
The Applied Natural Sciences and Technicology will 
form the two great divisions in the exhibition. It is in 
these two branches of social life that England has given 
so great an impulse to its own people, and is able to do 
the same in the case of other nations. 
The exhibition is not a commercial undertaking. Its 
idea has been started, and is being carried out, by men 
devoted to science and art, who have accordingly based 
it, not on the principle of competition, but on that of pre- 
vious invitation, and selection by competent judges. 
In view of the proposed formation of a Polytechnic 
Museum in Moscow, the Committee will also take the 
necessary measures that articles considered essential to 
form parts of a systematic collection in it, should be, 
if possible, secured for the museum. 

SOLAR RADIATION TEMPERATURES 
i, NATURE of August 24th, page 325, you quote the 
sun and shade temperatures published by Mr. H. 
Steward and Mr, F. Nunes, of Chiselhurst, and conclude 

with the following sentence—“ Surely there must be an 
error somewhere. The maximum temperature of Mr. S. 
or Mr. N. differ by 40° and 50°! Who is to teach or 
correct amateur meteorologists?” With your permission 
I will endeavour (1) to explain the possible cause of these 
discrepancies, (2) to show that it is to “ amateur meteoro- 
logists” a/one that we are ind¢ bted for (a) all published in- 
formation on the subject, and (g) for the inauguration of 
a system of strictly comparable observations on the tem- 
perature of the sun. 
The difference between a thermometer in sun and shade 
may I suppose be roughly defined as due to the excess of 
the heat rays which penetrate the former beyond those 
with which it can part. A bright, clear, glass bulb filled 
with mercury is evidently a mirror; it therefore reflects 
nearly all the heat rays which fall upon it, and therefore 
reads nearly the same in full blaze of the sun as in perfect 
shade. Hence it is useless as a measure of solar heat, 
and so long back as 1835 it was supplanted by a thermo- 
meter of which the bulb was blown in black glass. The 
next improvement was placing the thermometer inside a 
glass jacket, which was suggested about the year 1860, 
The reason for this arrangement was very simple ; the 
naked black bulb thermometer varied with every change 
of force in the wind, and no two instruments were com- 
parable, because it was impossible to secure precisely 
similar currents over both thermometers. The glass 
shields have greatly diminished, but not removed, this 
source oferror. The next improvement was to substitute 
a dull coating of black for the glassy surface which still 
acted as a partial reflector. Lastly, it was found that the 
unblackened stem of the thermometer reduced slightly the 
temperature of the bulb. Hence we arrive at the present 
form of instrument, a maximum thermometer, with its 
bulb and part of the stem dull blackened, enclosed in a 
glass shield or jacket. Most of them are at present made 
with nearly all the air exhausted from the shield (whence 
the term vacuum thermometers), but experiments are in 
progress with non-exhausted jackets, and that point must 
therefore be left open. 
The difference between one of the earliest and one of 
the latest form of instruments will reach 60° or 70°. 
It was supposed that position did not affect these im- 
proved instruments, and so (for example) we have that at 
Greenwich lying on grass, that at Oxford “in a niche in 
the west front of the observatory about five feet from the 
ground.”* Some experiments made by myself in 1867 
showed that the temperatures on grass depended on the 
state of the grass, whether succulent or parched, and on 
its length. Hence it was evident that here again compar- 
ability was gone. After many experiments by the Rev. 
F. W. Stow and others, one of his suggestions was 
adopted, and the thermometer placed on a post at the 
same height (4 ft.) as everybody (except the Meteorological 
Committee) places their shade thermometers. 
Having thus epitomised the progress of solar tempera- 
ture observations, I proceed very briefly to the points 
already mentioned. 
(1.) Explanation of the discrepancies. 
TEMPERATURE IN SUN DURING AuGuST, 1871 

Observer . |Mr. Steward) Mr. Nunes | Roy. Ob. Mr. Symons 



Locality. . . —- Chiselhurst | Greenwich | Camcen Squate 
Mode of Obser- r rH ../4ft. above 
aay Vac. | On Grass | OnGrass |On Grass 
_yation’. . sat | et | | ground. 
deg. | deg. deg. | deg. | deg. 
August 7. .| 113 | 148'o 1369 127°4 124°5 
Ay mest] 113 | 1470 130°5 | 120°2 1233 
Fre Oho 110 1515 1429 128'5 122'0 
yy IOs . 112 148'0 14273 | 124°5 1223 
BAP eG ae 119 150°7 140'0 124°3 118°4 
SAI 115 146°5 146 5 126°4 1225 
Ee 125 147'0 1510 | 128'0 126°2 
Mean . 122°4 1484 1414 | 1256 122°7 

The instruments and their position at Chiselhurst, 
* Radcliffe Met. Obs. 1867, page 4. 
