All the precautions of the Bank take time to operate.
The principal precaution is a rise in the rate of discount, and such a rise certainly does attract money from the Continent and from all the world much faster than could have been anticipated.

But it does not act instantaneously; even the right rate, the ultimately attractive rate, requires an interval for its action, and before the money can come here.

And the right rate is often not discovered for some time.

It requires several 'moves,' as the phrase goes, several augmentations of the rate of discount by the Bank, before the really effectual rate is reached, and in the mean time bullion is ebbing away and the 'reserve' is diminishing.

Unless, therefore, in times without precaution the actual reserve exceed the 'apprehension minimum' by at least the amount which may be taken away in the inevitable interval, and before the available precautions begin to operate, the rule prescribed will be infringed, and the actual reserve will be less than the 'apprehension' minimum.