52s L. W. Meech on the Sun’s Daily Intensity. 2 
assigned part of the day. The sun’s declination has” sa. Pe 
taken as constant, and it might easily be shown that what the » ’ 
sun radiates by rising earlier than the implied time, is compensa- 
ted ee a uniform change of declination producing an earlier set- 
ting su 
For teiting this frien, the intensities were computed foi the 
15th day of each month, on the latitude of Mendon, Mass.; ‘an 
the results were found to agree very —— with those observed: 
at that place about one month later,* as follows: the observed 
values are taken from the American Ansan for 1849, and are 
derived from fifteen years’ observations. 
Computed values. Observed values. | | Difference. 
seer aaa 0 | 28°38 24°.3, Feb 15,..; +190 
February-15,:...... 7142 33°.1 $3°.5, March 15,.< + A 
March 15, 9764 45°.2 45°.8, April 15,732.24 6 
April ie ek 12574 58°.3 557.0, May 16) 325s « 6° 
May lias 14482 67°.1 64°.5, June 15, . 34 2°65 
dune Mi vaccines se 15346 | 71°1 | 71°98, July 15,...... +4 
SUT oo oars Gees 15085 69°.9 68°.9, August 15, Lp anf) 
A SIG. esis 134387 62°.3 61°.0, September 15,. pe 
September 1G) eacis « 10860 50°.3 48°.5, October 15,...| ~—19.8 
Qetober 25... 0... 8080 B7c5 38°.9, November 15,./ -+1°4 
November 15, ..... 5638 26°.1 27°.7, December gh -| $19.6 
December 15, ..... 4510 20°.9 26°.0, January 1 +591 
It may be proper to observe that the preceding formula was 
divided by sin L, a constant factor ; and the numbers in the second 
column were then successively computed : their sum divided by 
twelve, gave 10163 as the mean, to be compared with 479.1, the 
observed mean at Mendon. Then as 10163: 479.1 :: 5040: 23°.3, 
Jan. 15, ete. Let it also be observed, that the Mendon values 
are the monthly means, which do not always fall on the 15th 
day, but nearly so. 
Before applying the formula further, let it be er by 
means of the astronomic equation, —cos H=tan nD. 
Dividing and multiplying the above intensity 7 sin D sin L, 
and at the same time substituting —cosH for its equal; and tan H, 
Daily intensity = 4? sin L sin D (H —tan H). (5.) 
This expression is much simpler than the one before employed, 
and by thus computing the temperatures for different places, and 
comparing the results with those actually observed, the extent of 
local causes will be disclo ste The ease with which daily and 
monthly temperatures ma w be computed, it is believed will 
render this formula Vitoable i in meteorological researches. It is 
* Since writing the above, I find it grgheg A — that the observed epochs of 
_ Maximum and minimum tempera rature in the th Temperate Zone fall about a 
assigned for this 
Besos The reason 
is, that for about a month after the summer solstice, the eaten con- 
rag Saga 
t 
tinues to receive feng y more heat than it loses at night; and conversely 
after the winter sol » it loses mo td 
the day. 
