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of a severe frost is the setting in of a N.E. wind if it be accompanied by a green or yellowish green sky, and the break up is all the more certain if the sky becomes gradually overcast and the wind backs from N.E. to N. and N.W.
Of S.E. wind there are two distinct kinds, one with a low barometer accompanied by warmth and moisture, ending in rainy or stormy weather. The other with a high barometer rising or stationary, and accompanied by dry weather and a clear sky which may be expected to last some time. Prolonged absence of wind is favourable to the prevalence of epidemics; but during continued windy weather, no disease arising out of local causes, such as deficient water or drainage, can be expected to make much progress.
In England windy weather is most common in December and January; then in February and November. The calmest months are August and September.
In England S.-Westerly winds prevail most; hence it may be inferred why the W. end is so often the fashionable quarter of large towns, because smoke, &c., is driven from the W. towards the E. Such a current not only carries away from the W. its own smoke, but keeps away altogether smoke contributed by Eastern districts.
The following represents the prevalence of wind in England on an average of years :—
| N. | 41 | S.E. | 20 | W. | 38 |
| N.E. | 48 | S. | 34 | N.W. | 24 |
| E. | 23 | S.W. | 104 | Calm | 33 |
