Causes of Immigration The causes of immigration are, of course,
yet harder to diagnose for us islanders, and we get little or no help from the Continent. No one, so far as I am aware, has so much as suggested a reason why white butter- flies in their millions and Clouded Yellows and Humming Bird Hawk moths in their thousands have undertaken the dangerous and, one would say, useless journey across the North Sea and the Channel. Omnia exeunt in mysterium; their exits and entrances remain a mystery. In smaller, more local statistics, reasons that make for success or failure are almost equally hard to manufacture. The population of partridges, for example, is quite inexplicably patchy. The coveys are large and numerous on one farm or estate and hardly discoverable next door. On the one the majority of birds shot are young ; on the other all are old. Wild pheasants on the other hand seem to have done well all round. As to grouse (of which Balmoral supplied a satisfactory quota), they are not everywhere numerous, but on the whole seem to be recovering from the melancholy deficiencies of recent years. In this case perhaps we may conclude that a revived war against vermin is having its effect.