YEATS, as you no doubt remember, had a hankering to be up and off to an island on a lake in Co Sligo, there to live in a mud cabin, growing beans and listening to the buzz of bumble bees.
I hear lake water lapping with low sounds by the shore, he used to say at the most unlikely moments, adding by way of emphasis
While I stand on the mad way, or on the pavements gray,
I hear it in the deep heart's core.
Now the local climate of Yeat's idyllic retreat would have been greatly affected by the lake surrounding it, the exact nature of this influence depending on the depth of water. Water acts like a storage heater, responding only very slowly to changes in the temperature of its surroundings. A goodsized area of deep water, therefore, tends to moderate the local climate, protecting it from the extremes to which it might otherwise be subject, while shallow water is less effective as a regulator, since it adapts to the prevailing temperature relatively quickly.
On a hot summer day the air over deep water remains relatively cold, and so a gentle cooling lake breeze, like a miniature sea breeze, may develop to waft lightly onto the adjacent land. Air that moves shorewards in this way is generally rich in moisture, and enhances any clouds tending to form some distance inland from the shoreline. The shorebound air, moreover, must be replaced by air sinking down towards the lake from higher levels in the atmosphere, so lakes tend to be areas of subsidence. And consequently, since clouds are associated with rising rather than sinking air, the skies above a large expanse of water tend to remain relatively cloud free compared to the surrounding countryside.
This effect is particularly noticeable in spring and early summer, when any rise in temperature experienced by the water lags far behind that of the adjacent land. In autumn and winter, however, these processes tend to be reversed, and cloudiness tends to be greater over and near a water surface than elsewhere. In a similar way, cold nights produce the opposite effect to a warm sunny day; a light current of cool air can be felt drifting out onto the surface of the lake to replace any relatively warmer air over the water itself that has succumbed to a tendency to float upwards.
Yeats however, would have had one clear advantage in his new wattle and daub existence; because of the moderating influence of the surrounding water, his nine beanrows would have been much less subject to frost than had he planted them elsewhere.