The exploits of the rebel steamer Alabama, so destructive to our commerce and so humiliating to our pride as a great naval power, sufficiently attest the vital importance of the element of speed in ships of war. Her capacity under steam is beyond that of our best vessels, and she therefore becomes, at her pleasure, utterly inaccessible to anything we may send to pursue her. We have built our steamers strong and heavy; but proportionately slow and clumsy. The Alabama could not safely encounter any one of them entitled to the name of a regular cruiser; but she does not intend to risk such a contest, and, most unfortunately for us, she cannot be compelled to meet it. Of what real use are all the costly structures of our navy with the tremendous ordnance which they carry, if this comparatively insignificant craft can go and come when and where she will, and sail through and around our fleets without the possibility of being interrupted? They are perfectly well suited to remain stationary and aid us in blockading the Southern ports; but the frequent escape of fast steamers running the blockade, serves still further to demonstrate the great and palpable deficiency in the speed of our ships of war. We may start a hundred of our best steamers on the track of the Alabama, and, without an accident, they can never overtake her. The only alternative is to accept the lesson which her example teaches, and to surpass her in those qualities which constitute her efficiency and make her formidable as a foe. This we must do, or we must quietly surrender our commerce to her infamous depredations, and acknowledge ourselves beaten on the seas by the rebel confederacy without an open port, and without anything worthy to be called a navy. The ability of our naval heroes, and their skill and valor, so nobly illustrated on several occasions during the present war, will be utterly unavailing against superior celerity of motion. Their just pride must be humbled, and their patriotic hearts must chafe with vexation, so long as the terrible rebel rover continues to command the seas, as she will not fail to do so long as we are unable to cope with her in activity and speed. Nor is it certain we have yet known the worst. Ominous appearances abroad, and thick-coming rumors brought by every arrival, indicate the construction in England of numerous other ships like the Alabama, destined to run the blockade and afterward to join that renowned cruiser in her work of destruction. Stores of cotton held in Southern ports offer a temptation to the cupidity of foreign adventurers which will command capital to any amount, and the best skill of English engineers and builders will be enlisted to make the enterprise successful--a skill not embarrassed by bureaucratic inertia and stolidity.