In spite of the frightful extent of the damage, the _Titanic_, because of the great height to which her plated structure extended above the water-line, and the consequent large amount of reserve buoyancy which she possessed, would probably have remained afloat a great many hours longer than she did, had the deck to which her bulkheads extended been thoroughly watertight. As it was, this deck (upper deck E) was pierced by hatchways and stairways which, as the bow settled deeper and deeper, permitted the water to flow up over the deck and pass aft over the tops of the after bulkheads and so-called watertight compartments. See page 129. Now, it so happened that for the full length of the boiler-rooms there had been constructed on upper deck E what was known as the "working-crew alleyway." On the inboard side of this passage six non-watertight doors opened on to as many iron ladders leading down to the boiler-rooms. Not only were these doors non-watertight, but they consisted of a mere open frame or grating, this construction having been adopted, doubtless, for purposes of ventilation. Unfortunately, although there was a watertight door at the after end of this alleyway, there was none at its forward end. The water which boiled up from the forward flooded compartments, as it flowed aft, poured successively through the open grating of the alleyway doors, flooding the compartments below, one after the other. [Illustration: TITANIC 1912 MAURETANIA 1906 _Titanic_: Single skin, 16 compartments; _Mauretania_: double skin, 34 compartments. COMPARISON OF SUBDIVISION IN TWO FAMOUS SHIPS] It does not take a technically instructed mind to understand from this that the safety elements of the construction of the _Titanic_ were as faulty above the water-line as they were below it. The absence of an inner skin and the presence of these many openings in her bulkhead deck combined to sink this huge ship, whose reserve buoyancy must have amounted to at least 80,000 tons, in the brief space of two and one-half hours. Not until the designer, Mr. Andrews, had made known to the captain that the ship was doomed was the order given to man the lifeboats. The lifeboats, forsooth! Twenty of them in all with a maximum accommodation, if every one were loaded to its full capacity, of something over one thousand, for a ship's company that numbered 2,223 in all. Just here, in this very fatal discrepancy, is to be found proof of the widespread belief that a great ship like the _Titanic_ was practically unsinkable, and therefore in times of dire stress such as this, was well able to act as its own lifeboat until rescuing ships, summoned by wireless, should come to her aid.