The connexion between the velocity and the pressure of the wind is one that is not yet known with absolute certainty.  Many text-books on engineering give the relation P=.005 v^2 when P is the pressure in lb per sq. ft. and v the velocity in miles per hour.  The history of this untrue relation is curious.  It was given about the end of the 18th century as based on some experiments, but with a footnote stating that little reliance could be placed on it.  The statement without the qualifying note was copied from book to book, and at last received general acceptance.  There is no doubt that under average conditions of atmospheric density, the .005 should be replaced by .003, for many independent authorities using different methods have found values very close to this last figure.  It is probable that the wind pressure is not strictly proportional to the extent of the surface exposed.  Pressure plates are generally of moderate size, from a half or quarter of a sq. ft. up to two or three sq. ft., are round or square, and for these sizes, and shapes, and of course for a flat surface, the relation P=.003 v^2 is fairly correct.

In the tube anemometer also it is really the pressure that is measured, although the scale is usually graduated as a velocity scale.  In cases where the density of the air is not of average value, as on a high mountain, or with an exceptionally low barometer for example, an allowance must be made.  Approximately 1-1/2% should be added to the velocity recorded by a tube anemometer for each 1000 ft. that it stands above sea-level.

(W.H.  Di.)

ANEMONE, or WIND-FLOWER (from the Gr. [Greek:  anemos], wind), a genus of the buttercup order (Ranunculaceae), containing about ninety species in the north and south temperate zones. Anemone nemorosa, wood anemone, and A.  Pulsatilla, Pasque-flower, occur in Britain; the latter is found on chalk downs and limestone pastures in some of the more southern and eastern counties.  The plants are perennial herbs with an underground rootstock, and radical, more or less deeply cut, leaves.  The elongated flower stem bears one or several, white, red, blue or rarely yellow, flowers; there is an involucre of three leaflets below each flower.  The fruits often bear long hairy styles which aid their distribution by the wind.  Many of the species are favourite garden plants; among the best known is Anemone coronaria, often called the poppy anemone, a tuberous-rooted plant, with parsley-like divided leaves, and large showy poppy-like blossoms on stalks of from 6 to 9-in. high; the flowers are of various colours, but the principal are scarlet, crimson, blue, purple and white.  There are also double-flowered varieties, in which the stamens in the centre are replaced by a tuft of narrow petals.  It is an old garden favourite, and of the double forms there are named varieties.  They grow best in a loamy soil, enriched with well-rotted