We can therefore regard it only as a local force--fixed within the limits of the defence of this particular place--and our estimates must be made accordingly.
The average durability of ships of war in the British navy, has been variously stated at seven and eight years in time of war, and from ten to twelve and fourteen years in time of peace.

Mr.Perring, in his "Brief Inquiry," published in 1812, estimates the average durability at about eight years.

His calculations seem based upon authentic information.

A distinguished English writer has more recently arrived at the same result, from estimates based upon the returns of the Board of Admiralty during the period of the wars of the French Revolution.

The data in our own possession are less complete; the appropriations for _building_ and _repairing_ having been so expended as to render it impossible to draw any accurate line of distinction.