_that of absolutely sealing the exits, was the only radical cure for the evil_, but that there were very great difficulties to be overcome before such an operation could be successfully carried out.

He was shown the plan that had been prepared for a mechanical block of all the enemy North Sea bases, and he entirely concurred in the impracticability of carrying it out.

Such a plan had been advocated by some officers and by other people; it was, of course, most attractive in theory and appealed strongly to those who looked at the question superficially.

When, however, a definite operation came to be worked out in detail the difficulties became very apparent, and even enthusiastic supporters of the _idea_ were forced to change their views.

It was not a matter for surprise to me that the idea of sealing the exits from submarine bases was urged by so many people on both sides of the Atlantic.