Involute Course of the Storm-Wind. we. 
lines ; and the direction of wind at that hour, so far as deter- 
mined by direct or ens observation, is indicated by the 
several wind-arrow 
To avoid any ioe of error, the ee: delialeaitens are also 
made for different periods of the day, at intervals of three hours 
each ; which will be found on Charts V to X, inclusive:. These 
are drawn on the same scale and ground work as Chart IV, and 
are severally derived in like manner from the observations. This 
will afford opportunity for mariners and others to contemplate 
the progressive changes which are produced, on different sides, 
by the advance of the revolving storm. | 
~ This manner of plotting the simultaneous observations, for in- 
spection, was adopted in my notice of the New England storm 
of Dec. 15th, 1839 ; but without the advantages of a successive 
* 
exhibition at daily intervals, which the present case affor 
If any inquirer, who is careful to apprehend rightly the several 
accounts relating to the wind’s direction, and the true periods of 
the several successive changes there mentioned, shall conclude 
that any of the wind-arrows found on these Charts are without 
sufficient authority, he has only to cancel the same and rely on 
those others which he may deem to be more truly determinate ; 
and it will easily be seen whether the proof of a general rotation 
of the storm-wind is at all invalidated by such omissions. 
~Vortican Incuinatton or tHE Storm-Wiyv.—By this is 
meant some degree of involution from a true circular course. 
In the New England storm above referred to, this convergence of 
the surface winds appeared equal to an average of about six de- 
grees from a circle. In the present case, such inclination seems 
more or less apparent in the arrows on the storm figures of the 
several charts; where the concentrical circles afford us means for 
a just comparison of the general course of wind which is approx- 
imately shown by the several observations. In some quadrants 
of the storm, as thus exhibited, the average inward convergence, 
at certain periods, may amount to two or more points of the com- 
pass. This may possibly be due in part, to the trending of the 
coast, and also more probably to the very prevalent habit of re- 
* This Journal, vol. xlii, p. 117. Trans. Am. Phil. Soc., vol. viii, part i, p. 81. 
Scam vol. i, Second Series, p- 14. - 
