This "defensive moat" has always proved a barrier against foreign attack, but it has not preserved our islands from invasion. Celts, Romans, English, Danes, and Normans have in turn conquered England; but never since it became the home of a united nation with a strong Navy has any foreign invader landed in strength on our shores. For more than eight hundred years no hostile army has dared to invade us, and our people have never been forced to lay down their tools and snatch up their weapons to drive away the invader. No other land in Europe can make this boast. We owe this long reign of security to our Navy. Not only has our Navy kept us free from invasion, but by winning for us the mastery of the sea it has enabled us to build up a great foreign trade, by which we have grown rich and great, and to found colonies and hold possessions in every continent on the face of the globe. At the present time it does even more than this--it secures for us the means whereby we live and move and have our being. So many of our people are now engaged in mines and quarries and factories, on railways, and in offices, that we do not grow enough food for our needs. There is never enough food in this country to last our people for more than a couple of months or so. We draw our food supplies from all parts of the world, and were a foreign foe to destroy our Navy and cut off our food ships, the great bulk of us would soon perish of starvation. So you see that "Britannia _must_ rule the waves," if we are to exist at all and remain the greatest trading and colonial nation of the world, as we are to-day. Every sensible man understands this, and all agree that our Navy must be very strong and very efficient. It must be able to command the seas, for, as Raleigh told us long ago, "Whosoever commands the sea commands the trade; whosoever commands the trade of the world commands the riches of the world, and, consequently, the world itself." [Illustration: H.M.S. Colossus firing a salute. _Photo, Cribb._] [Illustration: The sure shield of Britain--a scene at the Naval Review. _Photo, Cribb._] Never has the British Navy been so powerful and so well equipped both in ships and guns and men as at present. The "wooden walls" in which Blake and Nelson fought have long since disappeared, and our bluejackets now fight behind bulwarks of steel. Steam has taken the place of sail; the old muzzle-loading guns have been superseded by huge weapons, the largest of which can hurl nearly a ton of metal for twelve miles with deadly aim. Our modern warships are filled with costly machinery quite unknown and even undreamt of in the days when Britain fought and won the greatest sea fights of her history. But though the ships have changed out of knowledge, the officers, bluejackets, and marines who man them possess all the old fighting spirit and all the courage and daring of their forefathers.