124 
The arrows show the direction of the current ; and 
Euclid’s proposition as to parallelograms about the 
diagonal of a parallelogram shows at once the application 
of the first law of Thermodynamics to the figure, as the 
Electromotive force together with the Peltier effect at the 
cold junction obviously amount to the sum of the two 
Thomson effects and the Peltier effect at the hot junc- 
tion. 
Also, if we suppose the lines AD, BC, to be very 
close to one another, since we have always A D =7 
we get(BC—AD)¢= #a(7) = — (a, — o,)8¢, whose appli- 
cation to the second law is obvious. The reader may 
easily construct for himself diagrams for other cases of 
relation of the temperatures of the junctions to that of 
the neutral point. 
Thomson’s original paper will be found in the 
Transactions of the foyal Society of Edinburgh, 
and farther details of my experimental work in recent 
numbers of the Proceedings ofthe same society. I 
may avail myself of this opportunity of asking assis- 
tance from men of science in procuring wires or foil 
of the more infusible metals, such as Cobalt, Chromium, 
Tungsten, &c, 
Ps Gk, 
THE LAW OF STORMS DEVELOPED* 
th 
ETEOROLOGISTS tell us that their science is as 
old as Aristotle. If we should judge by its pro- 
gress up to the middle of the present century, its antiquity 
furnishes little to boast of ; for, in the long lapse of cen- 
turies, it must have proved an incorrigibly dull scholar, 
Within the past few years, however, it has greatly im- 
proved, and, especially since it became identified with the 
popular and important systems of storm-warnings and 
weather-forecasts, it has been rapidly developed. This is 
peculiarly the case in America, and it is not wonderful, 
when we consider the comprehensive observations of our 
meteorological bureau, and the many beautiful phenomena 
which its publications disclose. 
If Vasco Nunez, the discoverer of the great South Sea, 
was so awed by the grandeur and expanse of its waters, 
as seen with the naked eye, how much more may we be im- 
pressed as telegraphic meteorology enables us to discover, 
at a glance, the tossings and undulations of the aérial 
ocean over the larger part of the hemisphere ! 
It is to some of the deductions, that may be justly 
made from the extensive and synchronous observations 
of the modern weather-systems, as they bear upon those 
weather-problems, which, from time immemorial, have 
interested mankind, that we now ask attention. 
Until the year 1821, “the law of storms,” simple as it 
is, was unknown to the most profound meteorologists and 
expert seamen of the world. It was then first discovered 
and announced by Mr. William C. Redfield, of New York, 
and established by the labours of that great mind, against 
the constant perversions and opposition of the scientific 
empirics of his day. It can be easily comprehended in 
its great outlines, and as far as our present purposes re- 
quire, It assumes nothing, supposes nothing ; but, from 
thousands of actual and actually recorded observations, 
presents the phenomena of spiral currents of air seeking 
a common centre of depression, and, in the attempt to 
find that centre, acquiring a vorticose or rotatory motion, 
The direction of this rotation Mr, Redfield found to be 
uniformly, in our hemisphere, contrary to that of the 
hands of a watch, with its face turned upward ; and, in 
* From the Popular Science’ Monthly. Communicated by the author, 
Prof. Thompson B. Maury, of the Signal Office, Washington. 
Se Re CPE > eT Me Te 
NATURE 
[Fuse 12, 1873 ; 
the Southern Hemisphere, the rotation is with those 
hands, or with the sun in its diurnal round. It is easy to 
see that, if the atmospheric column, resting over any 
given area of the earth’s surface, should, from any cause, 
be suddenly diminished, or its pressure and intensity be 
reduced, the gaseous fluid would rush in from all sur- 
rounding regions to restore the disturbed equilibrium ; 
and if the earth was not whisling around on its axis, 
every particle of the centre-seeking air would endeavour 
to move on the shortest, or the straight line. It is known, 
from the principles of mechanics, that this endeavour can 
never strictly be executed, because the axial rotation of 
the globe incessantly so acts as to throw every body, 
while in motion, in our hemisphere, to the s7g/#¢ of the 
line on which it is moving, no matter whether that line be 
from east to west, north to south, or at any conceivable 
angle with the meridians or the equator. Obeying, in 
part, this tangential impulse, every particle of wind must 
take up a resultant motion. If it begins to blow toward 
the depressed centre of the storm as a north wind, it 
trends to the west, and is felt as a northeaster ; if it 
begins as a south wind, it diverges as a southwester ; if 
as an east wind, it becomes a southeaster ; and, if as 
a west wind, it soon changes into the boreal northwest 
wind. 
It has often been asked whether the storms of our lati- 
tudes attain the immense size formerly attributed to 
them ; and many eminent writers have denied the possi- 
bility of their reaching a diameter of more than two or 
three hundred miles. Mr. J. K. Laughton, in his recently- 
published “ Physical Geography,” would have us believe 
that cyclones “do not attain the enormous magnitudes 
which have been assigned them.” But this opinion rests 
merely upon conjecture, not yet upon a correct physical 
theory. 
It is a well-known fact that the monsoons generated 
on the central plateau north of the Himalaya Moun- 
tains, and the whole system of Asiatic wet monsoons, 
may be regarded as an immense and prolonged cy- 
clone; extend their “backing” influence into the 
Indian Ocean, and reach far to the south, through 
more than forty degrees of latitude (a radius of 2,500 
geographical miles), and from the 60th to the 14oth | 
meridian of east longitude, far out into the Pacific, | 
beyond the Bonin and Ladrone Islands, southeast of 
Japan. The whole system of wet monsoons may also 
be justly regarded as a grand cyclone, whose centre 
is stationary over the heated plains of Central Asia, 
whose intro-moving winds, bearing the evaporations of 
the Asiatic seas and oceans, feed it with meteoric fuel for 
six months in the year, and whose periphery may be re- ; 
garded as embracing nearly one-third of the entire eastern 
hemisphere. Analogy, therefore, warrants the idea of a 
great cyclone. But, apart from all this, actual observa- 
tions in different parts of the globe prove the frequency of 
storms of enormous magnitude. Thus, in the celebrated 
Gulf-stream storm of 1839, as Sir David Brewster long 
ago pointed out, several staunch merchantmen were foun- 
dering off the coast of Georgia, near Savannah, in the 
very heart of the gale, at the same hour that the winds in 
its north-west quadrant were taking the roofs off houses 
in New York and Boston, more than 800 miles distant— 
clearly revealing a cyclone whose formation was symme-, 
trical, and whose diameter must have been nearly 1,300 
miles. But, not to go back to old data, the West-Indian 
storm of August 18, 1871, before its centre had moved 
north of Florida, had begun to draw upon the regions of 
high barometer in the Northern States, had exerted its 
influence as far north as New London, Connecticut, and 
gave us the north-easterly cyclonic winds in the north- 
west quadrant of the whirl, on the entire Atlantic coast. 
The more furious cyclone of August 24, 1871, discovered 
to be then south-east of Florida, and telegraphically fore- 
announced as likely to endanger the coasts of the Southern 
q 
