Hot-horse anemometry

LETTER

TO THE EDITORS

HOT-HORSE

ations in temperature. The thermal inertia of ths statue acts as a low pass tiller, so that the turb.ulence o>e: pnods of a few minutes is evident. May H-e consider it a< x example oi hot-horse anemometm?

XNEMOMETRY

Regarding the dependence of lateral turbulence on sampling pried, I enclose as a curiosity the record of the surface :emprrature (Fig. I) of the bronze horses of St Mark at Venice (Fig. 2). The bronze exposed to the direct solar radiation at mid-day becomes about 15. C warmer than the atmosphere. so that fluctuations in wind speed cause fluctu-

Fig. 1. Surface temperature of one of the bronze horses during a clear day (4 August 1974). In the early morning and at about 10.30 LST the horse is covered by the shadow of cusps of the Basilica of St Mark, and at 13. I5 LST by the shadow of the bell tower. During the night the temperatures of the Horses and of the air become practically equal and without fluctuations.

Fig. 2. The bronze

horses,

Basilica of St Mark, Venice.