We will now make the calculation for the central vortex _descending_,
for longitude 88d 50' west, August 7, 1853,--putting down the necessary
elements for the time of the meridian passage in order:
Meridian passage in local time at 2h. 25m. P.M.
" " in Greenwich time 7d. 8h. 18m.
Mass of the moon 1/12.3 M. R. V. minor 3,256 miles.
Obliquity of the vortex, same time 26d 5' 0"
Polar angle of " " 17 41 47
True longitude of moon's node " 78 42 0
" inclination of orbit " 5 5 0
" longitude of the sun " 135 20 0
Moon's longitude " 169 44 0
" distance from node " 91 2 0
" distance from quadrature " 55 36 0
" true semi-diameter " 943
" right ascension " 172 30 0
" declination north " 8 42 20
Constant logarithm 2.889214
Arith. comp. of log. of 943 7.025488
Log. cos. arc. AR 9.914702 = 34d 44' 48"
1st. correction, + 2 45 0
2d. correction, - 1 14 15
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Corrected arc AQ = 36 15 33
PA = 81d 17' 40"
PV = 26 5 0
P = 115 11 47
V = 63 34 26
A = 23 28 24
AV = 92 48 39
Q = 31 32 18
Complement of lat. = PQ = 48d 49' 41"
The latitude is therefore for
the earth, as a sphere 41 10 18
Correction for protuberance + 0 16 0
------------
True latitude of centre 41 26 18 north.
------------
Latitude of Ottowa 41 20 0 "
------------
Vortex passed 6 18 north of Ottowa.
[Illustration: Fig. 16]
As this was nearly a central passage, and as the influence was less
extensive than usual, on account of great atmospheric pressure with a
low dew point, the central disturbance could the more readily be
located, and was certainly to the north, and but a few miles. The
following is from the record of the weather:
_August_ 6th. Very fine and clear all day; wind from S.-W.; a light
breeze; 8 P.M. frequent flashes of lightning in the northern sky;
10 P.M. a _low bank of dense clouds in north_, fringed with cirri,
visible during the flash of the lightning; 12 P.M. same continues.
7th. Very line and clear morning; wind S.-W. moderate; noon, clouds
accumulating in the northern half of the sky; wind fresher S.-W.; 3 P.M.
a clap of thunder overhead, and black cumuli in west, north, and east;
4 P.M. much thunder, and scattered showers; six miles west rained very
heavily; 6 P.M. the heavy clouds passing over to the south; 10 P.M.
clear again in north.
_August_ 8th. Clear all day; wind the same (S.-W.); a hazy bank visible
all along on _southern horizon_.
This was not a storm, in the ordinary acceptation of the term; but the
same cause, under other circumstances, would have produced one; and let
it be borne in mind, that although the moon is the chief disturbing
cause, and the passages of the vortices are the periods of greatest
commotion in both settled and unsettled weather, still the sun is
powerful in predisposing the circumstances, whether favorable or
unfavorable; and as there is no periodic connection between the passage
of a vortex and the concurrence of the great atmospheric waves, it will,
of course, happen only occasionally that all the circumstances will
conspire to make a storm. There are also other modifying causes, to
which we have not yet alluded, which influence the storms at different
seasons of the year,--exaggerating their activity in some latitudes, and
diminishing it in other latitudes. In this latitude, the months of May,
June, and July are marked by more energetic action than August,
September, and October. The activity of one vortex also, in one place,
seems to modify the activity of another vortex in another place. But the
great question to decide is: Do these vortices really exist? Do they
follow each other in the _order_ indicated by the theory? Do they pass
from south to north, and from north to south, at the _times_ indicated
by the theory? Do they obey, in their monthly revolutions, a
mathematical law connecting them with the motions of the moon? We answer
emphatically, Yes! And the non-discovery of these facts, is one of the
most humiliating features of the present age.