March 3, 1871.] 40) (Chase. 
American Weather Notes. 
By Puiny EarLE CHAse. 
The signal service observations of our War Department have already 
N 
shown the value both of Buys Ballot’s law and of Capt. Toynbee’s modi- 
fication in predicting changes of wind, especially if due regard is paid to 
the barometric variations of the two previous days. They have also 
suggested the following general deductions, some of which may perhaps 
prove to be true only of the winter, while others seem to be explicable by 
natural circumstances of position and physical configuration, which must 
be operative at all seasons. 
1. Winds varying like the land and sea breezes, are often traceable, 
especially in the lull which follows the passage of storms, to differences of 
temperature in the neighborhood of the great lakes, and of mountain 
peaks and ridges. 
2. The wind, especially in the Southern States, often blows directly in 
the line of the greatest barometric gradient. But even in such cases, 
after a few hours continuance, it tends towards the azimuth indicated by 
Buys Ballot’s law. 
3. The isobaric lines are, therefore, often of less relative importance 
than the gradients in forming forceasts. 
4, Long ridges of high barometer, as observed by Espy and others, 
with adjacent troughs of low barometer, often traverse the continent, 
sometimes with slight defiection, sometimes having a semi-circular, 
cireular, or elliptical curvature with a diameter of three thousand miles 
or more. Such ridges usually have a steeper declivity and stronger winds 
on their northerly and easterly than on their southerly and westerly sides. 
5. Currents with an anti-cyclonic tendency, controlled by arreas of high 
barometer, are notably common. Reversals of wind, asfrom N. E. to8. W.., 
are, therefore, frequent after the passage of an anticyclonic ridge or cen- 
tre, as well as after the passage of a cyclone. 
6. Our recent storms have been anticyclonic, and there seems some 
reason for supposing that anticyclones are the usual “ weather-breeders,’” 
even of such of our land storms as become more or less cyclonic after they 
are fully developed. 
7. The precipitation of vapor of course gives rise to local cyclones, 
which, however, may be easily and speedily overborne by the grand anti- 
cyclonic whirls of a half million miles or more in area. ’ 
8. These and other peculiarities, point to a probable origin of storms 
in the blending of polar and equatorial currents, near the latitudes at 
which the general tendency of the winds changes its direction. 
9. Mr. Scott has observed that when polar (E.) currents are blowing at. 
the North, and equatorial (W.) currents at the South, a serious baro- 
metrical disturbance, frequently resulting in a gale, generally soon fol- 
lows ; but when the polar current is at the South and the equatorial at 
the North there appears to be no law of sequence. The latter condition, 
with us, seems often indicative of approaching fair weather, especially if 
northerly or easterly are separated from southerly or westerly winds by a 
ridge of high barometer. : 
10. If the progress of a northerly or easterly current towards the equa- 
tor is impeded by an intervening southerly or westerly current, the dis- 
turbance not only speedily follows, as indicated by Mr. Scott, but it is 
also, commonly, like most showers, 8. JJ. storms, and other marked cyclonic 
commotions, of briefer duration than those which are primarily anti- 
cyclonic. 
; 
Hs, 
