Be a 
ern hemisphere 4? is as 
© LW. Meech on the Sun’s Daily Intensity. 53 
to be, mentioned here, that H is an are of a circle whose radius is 
‘1, which will readily be found by reducing the degrees and min- 
Aites, to minutes, and multiplying them by sin 1’, or by multiply- 
ing the minutes in time by sin 15’; also using the natural tangent 
_ of H, with its trigonometric sign. When the computation is for 
_ one place only, sinL being a constant factor may be rejected, 
‘leaving, 
Daily intensity =? sin D(H —tan H.) (6.) 
For example, the results are subjoined for Calcutta, in latitude 
2° 35’ N.; the observed temperatures follow the computed, in 
order :-— 
January, 59°.2; 65°.1 | July, 92°.3; 829.6 
February, 69°.2; 70°.0 August, 88°.9 ; 82.9: 
March 197,63: 780.4 September, 82°.5; 82°.4 
April, 88°.0; 839.3. | October, 72°.6; 81°.0 
May, 92°.0; 85°.5 | November, 61°.8; 73°.4 
June, 93°.1; 849.7 | December, 56°.2; 66°.6 
From this it appears, that at midsummer about one-tenth of 
the heat received is carried away by those upward currents which 
produce the trade-winds, by sea-breezes, and the conducting 
power of the soil; also a less quantity of heat is restored by the 
ground, and by winds in mid-winter. 
IV, Is the temperature of summer and of winter in the south- 
ern hemisphere, the same as with us, at equal latitudes? On this 
point, the formula cos H=—tan L tan D, clearly shows that the 
length of the day there is the same as in the northern hemi- 
Sphere six mouths later. The difference of temperature is there- 
fore limited to the values of 4?. Now the earth being nearest 
the sun at the northern mid-winter or on January Ist, 4? is at 
a = ; while at mid-winter in the south- 
that time measured by 
: . : de 
(The The difference is ne) 
or the proportional difference, taking our mid-winter’s tempera- 
bed = de — 8e? +.,.=0:06 nearly. 
1+e)? 
- The southern mid-winter is therefore from 1° to 2° colder; and 
per year, which in time will return to the southern hemisphere 
the advantage Wwe now possess. The summer season of the 
southern temperate zone being hotter, is also shorter by about 
eight days than in the northern hemisphere ; which difference is 
ascribed to the more rapid motion of the earth about the perigee. 
