MAGAZINE OP SCIENCE AND ART. 
Cl 
very small intensity of heat, while on the contrary to 
render it capable of registering large quantities of radi¬ 
ant heat without requiring to fee reset, wo may contract 
the evaporating surface to an almost indefinite extent. 
Thus we might have sun-gauges specially adapted for 
registering all the sun-shine during a month or week, 
or merely one day, and only requiring to be read off 
and reset at the ends of those periods. Lastly, we 
might have an instrument so delicate as to give accurate 
results during a single minute of time, thus to deter¬ 
mine, like .Sir J. Herchel’s actinornetcr, the absolute 
intensity of the sun’s heat at any moment of that time. 
Of course the indications of sun-gauges of such different 
sizes will not express uniform amounts of heat tilL they 
are reduced in the inverse proportion of the surfaces of 
evaporation , which must be previously measured with 
accuracy. 
The sun gauge as described would not be adapted for 
climates much colder than that of Australia, becauso 
the water contained in it would undoubtedly often 
freeze. Alcohol or some other liquid not easily frozen, 
should then he employed, and after taking into con¬ 
sideration the different latent heats of the vapours of 
these liquids, the action and results of the instrument 
would be just the same. 
A modified form of the instrument could easily be 
contrived to measure and register terrestrial radiation, 
or the coolin" of the surface of the earth at night by' the 
radiation of heat into empty space. The model of the 
sun-gauge, figure I, is often found to give distinct indi¬ 
cations of nocturnal radiation. 
To show the uses of this instrument, I may just re¬ 
mark in conclusion, that meteorology is a branch of 
science occupied with investigating the almost infinite 
complication of phenomena exhibited by two inert 
elements, air and water, under the xntiuence of that form 
of force and motion commonly called heat. By the 
action of heat on tlio atmosphere, all winds, storms, 
clouds, rain, anil in short all changes of differences of 
weather or climate are in a more or less direct manner 
produced. The sun is the solo source of al l the heat 
engaged in these effects, but tbe quantity and intensity 
of liis rays, which reach and act on the’ surface of the 
earth at any' given place or time, are regulated by many 
circumstances, of which the principal are— 
1 st, The latitude of the place, upon which depends 
the elevation of the snn and the length of the dav. 
2nd, The imperfect transparency of atmospheric air. 
3rd, The screening effect of clouds. 
4th, The difference of the absorbent properties of the 
ground, ocean, &c. 
To estimare the effects all these circumstances pro¬ 
duce would be clearly' impossible, and in order, there¬ 
fore, to take an account of all the supplies of heat which 
tke earth receives, it is necessary we should possess an 
instrument of a continuous character for measuring 
accumulated amounts of radient heat. Not only should 
we thus gain data most valuablu for disentangling the 
complicated causes and effects with which meteorology 
is engaged; hut, in a more popular point of view, the 
yearly or daily' average amount of sunshine would be a 
new element in the description of climates and localities. 
TABLE I. 
For Reducing Results of Sun Gauge. 
Temperature 
of air. 
Latent heat 
of vapour. 
Correction 
factor. 
32 degrees. 
1092 degrees. 
•ooo 
42 „ 
1085 „ 
•006 
52 „ 
1078 „ 
013 
02 „ 
1071 „ 
•020 
72 „ 
1004 „ 
•026 
82 „ 
1057 „ 
•032 
32 „ 
1050 „ 
•038 
102 „ 
1043 „ 
045 
It a = reading of sun gauge. 
True result = a — a a. correction-factor. 
TABLE II. 
Results of Hourly Observations with Sun Gauge 
DURING THREE DAYS. 
1857. 
Hours. 
Fob. 22. 
April 2G. 
June 21 . 
$ 
O 
H 
' 5 '§ 
"8 § 
3 g 
PS M 
2 3 
,<u 
<a 
8 
© 
fcn 
P 
to 
3 
Ul 
t*. 
o 
§ 
o 
3 
o 
3 
V—1 
Difference of thermometer 
in sun and shade. 
Indications of Sun gauge. 
© 
o 
3 © 
O rtf 
3 3 
Cl 
o § 
o rt 
S p 
p cn 
£ pi 
i§' 
8 
Indications of Sun gauge. 
A.M. 0.0 
•3 
0 
—•7 
0 
—29 
0 
7. 
22-1 
0 
434 
0 
—21 
0 
8.0 
32-0 
0 
7*5 
0 
+208 
0 
„ 9.0 
30-1 
4- 
292 
5 
22-8 
1 
„ 10.0 
372 
17- 
311 
13 
£3-6 
10 
„ n.o 
39-3 
22 * 
301 
18 
20-1 
13 
„ 12.0 
401 
22-5 
331 
18 
29-7 
13 
P.M. 1.0 
35-9 
19-5 
38-6 
18 
32-6 
13 
„ 2.0 
30-5 
17- 
39-4 
15 
32-4 
13 
„ 3.0 
179 
9- 
34-2 
15 
30-2 
8 
„ 4.0 
210 
2 
28-0 
8 
21-0 
5 
„ 5.0 
4-8 
0 
•8 
2 
—1-5 
0 
„ G.O 
•8 
0 . 
—1-4 
0.5 
—26 
0 
Means 
& Sums. 
24-4 
1130 
21-6 
1125 
| 17-7 
70 
N.B.—The place of observation is shaded till near 8 
a.m., hence the absence of indications before that hour. 
The first two days were a little cloudy. The mark —• 
indicates that the exposed or sun-thermometer read 
lower than the sheltered thermometer, which marks the 
temperature of the air. 
TABLE III. 
Results of a Few Daily Observations taken with 
the Sun Gauge on the undermentioned dates. 
S3 S 
p ©,a a 
p © * a 
1 § P° 
HgS* 
Mean extent of 
cloud. 
Indications of 
sun gauge. 
1857. 
June. 
P - 
U-"* © 
° g g -5 
© a 
p 2* p 
111 s 
S5c s 
•— Cl P 
i—t 
Mean extent of 
cloud. 
Indications of 
sun gauge. 
l 
Decrees. 
33* 
5 
251 
7 
Degrees. 
21 * 
i 
34 
2 
7- 
10 
129 
8 
2 * 
4 
37 
3 
10-5 
5 
68 
9 
23- 
4 
48 
4 
32- 
1 
208 
10 
13- 
4 
41 
5 
22 - 
9 
47 
11 
23- 
0 
24 
6 
5- 
0 
53 
12 
28- 
0 
26 
! 
33- 
4 
174 
13 
19* 
4 
47 
8 
30- 
6 
138 
14 
27- 
2 
61 
9 
9- 
10 
3 
15 
25- 
0 
48 
10 
5- 
10 
3 
10 
6- 
8 
0 
11 
20 - 
3 
152-5 
17 
Storm 
5 
14 
12 
11 - 
10 
8-5 
18 
25- 
7 
I 8 
13 
o- 
10 
5o 
19 
3- 
5 
14 
21-5 
4 
125 
20 
4 
10 
Means 
&sums 
17'5 
G-7 
1415 
18-0 
3-4 
398 
