Virginia Argus. [volume] (Richmond, Va.) 1796-1816, 1810-02-27

| i49O57 square miles. Bat an, equal
lPortion is not melted every day Is
manifest, for the quantity melted dali
ley increases, because the heat of the
sun rs proportional to its light, and its
Hight to the density of itsrays. The.
density of the SUMS rays not only daily.
varies, but differs according to the par
'lallel OF latitude. The nearer the sun
approaches the zenith, the more per-
}pendicuiar are his rays, and conse :
lquently the moro intense his heat.
| Della Methcrie in his tn cory of the,
earth (vol. 8, page 39l) has investiga-
ted at some length, the different causes
which afiectthe heat of the sun. Accor-
|ding to this writer, the four principal
|are, Isl, The suns altitude above the
horizon. FL. Theintensity Of rays,
I which varies with his altitude, on ac-
count ofthe extent Of the atmosphere
Through which they have to pass. Sd.
His distance from the earth. 4th. The
Iperiod of time which the sun remains
ABOVE the horizon.
| With respectt to the variation of the
suns heat according to his altitude,
DIR. HALEY and Fatio differed in opin;-
lon. The former contended, that the
suns heat increased in the simple ra !.
ito OF the sines;of his altitude; the lat
1 ter maintained, that his heat increased
IN the proportion of the squares of the
! sines. Marian endeavered to ascer-
TAIN the fact by experiment he took
4 mirrors of an equal size, from which
he reflected the rays of the sun upon
the bulb OF a thermometer one mir.
ror raised the fluid to three degrees.
two mirrors caused it to rise to SIX de,
| grees, and from the reelection of three
mirrors it roseIo nine degrees. from
| which simple experiment Marian con.
| cluded, that the heat produced by the
| rays os.the sun increased in the simple
ratio OF the attitudes.
i The intensity Of the suns ravs evil
] IDENTITY varies with his al:ituae (; hut it
/ is extremely diticult to ascertain the
law OF this variation. The intensity
here meant, is the intensity Of the RAYS
after having passed through the a.mos.
| sphere. Bouguer has furnished us
with table IN which he gives this in
tensity for the several attitudes ofthe
sun. He supposes the intensity of the
rays of the sun inlsaving the body of
the Mminary to be 10000, he tn n
hnds that IL the sun was ia the zenith,
the force of his rays at the surface
OF the earth would be diminished to
813e. AT the altitude of so degrees,
he calculates it would be reduced to
1924, and at the altitude of 25 degrees,
lit would=6136, In the latitude OF
Paris, he finds in the summer solstice
iit would be 7944 94-loe bat in the
| winter solstice 5O94 SO 100.
/ The third cause of the variation of
| the heat of the sun, viz: the change Of
distance from the earth,is also noticed
| oy Bouguer. In winter his distance
from the easth is 937so21o French
leagues, IN summer, ,34934726 leagues.
bat as he is longer in the northern
Hemisphere than In the southern, an
allowance Tor this ought to be made.
Taking both the causes into consider.
alton, Bouguer finds that the force Of
! the suns rays at the same altitude in
the summer solstice, i to their force
in the winter solstice, as sIf 10 900, or
nearly as Is to Is.
The fourth cause affects considera-
bly, the heat Of the sun /; for the logger
1.-THE sun remains above the horizon,
the more his action is prolonged.
Marian supposes it to be in the ratio
OF tue square of the time, although
from theory we might suppose it to be
only in the simple ratio of the times.
For a cause which acts two hours,
would seem capable Of only producing
double the effect of the action Of one
hour.
Combining together the effects pro-
dnced upon the solar heat from these
several causes, we may be warraated
in saying, that the quln,ity Of polar ice
melted every day from the 2tst OF
March until the summer solstice, in
creases at least in the ratio of the
squares OF the suns altitude, and from
ene summer solstice until the sutum.
pai equinox, in the ratio of the squares
lOf the times.
Therefor ifo1ffofoO H. ,,,,..t -