Page:The Migration of Birds - Thomas A Coward - 1912.pdf/117

Rh I have endeavoured to show that often the force of wind is greater at a high than st low altitude, and there is ample evidence to prove that birds fly at a great height when conditions are favourable. Birds usually leave Scandinavia when there are descending currents flowing outwards from the centre of high pressure; is it wild speculation' to suggest that it is the southward flowing currents, which are also deflected westwards, upon which the birds intend to travel? Thus the bulk of the Scandinavian birds might not touch Britain at all, but those which started upon light to moderate north-east to easterly winds from the western shores of Norway would be helped to Britain. Mr Clarke mentions that when he was at Fair island, north-west to westerly winds did not stop migration from the north, but is it certain that the birds did travel in or against these westerly winds? May they not actually have travelled on the "good side" of the cyclonic system, with these very winds carrying them towards Fair Island? their actual visible approach from the north does not prove that they had travelled all the way in this line.

On September 22nd, he says—"The favourable meteorological conditions of yesterday—fine weather and moderate south-east breezes,—has had a marked effect, for to-day golden-sets are swarming everywhere." But what does he mean? Favourable