To shew a light pair of heels. The phrase is applied as a reproach to persons leaving their posts and flying from the enemy instead of fighting.

A cask, when empty, may be rolled or moved from its place, by a slight impulse, but when filled, it is not to be moved but by the exertion of considerable force. The weak and uninformed man, like an empty vessel, may be turned from his purpose, by the most trifling and insignificant arguments, or rather, having no fixed principle of action, he is perpetually wavering, and changing his designs. But the considerate and wise man, having, on mature reflection, formed a plan for his conduct, like the well filled cask, he is not easily to be moved or deterred from pursuing his object.

«Though the whole frame of nature round him break,
He unconcerned will hear the mighty crack».

The adage is said to have taken its rise from a story told of Diogenes, the cynic. When the city of Abdera, in which he lived, was threatened with a siege, seeing the citizens running about confusedly, without order, or fixing on any plan for defending the place, he took the tub in which he lived into the market, and rolled it about with great vehemence, intimating that until they quieted the tumult and confusion that reigned in the city, they were equally insignificantly and unprofitably employed.