TIDAL HARBOURS                 255
between battleships, as was done on the 23rd, the number of vessels that can go out in one tide is limited. It may be recalled that when the squadron put to sea before war was declared the operation took three days. Even after the first losses it was unable to put to sea at one tide, and can only accomplish this feat to-day in five hours with the utmost difficulty.
These figures, assuming them to be correct, are exceedingly interesting, since they show that Port Arthur labours under the same disadvantages as many tidal harbours belonging to our European neighbours, and we are able for the first time to obtain positive proof of the grave defects of harbours of this character in time of war. To those who have studied these questions the facts are well known, but they are not known to the great body of the public. Warships coming out of tidal harbours can only do so at hours that can be exactly calculated by the enemy. When outside they must depart singly or await the appearance of their consorts. In the first case they can be attacked singly, and in the second they are exposed to the incidents we have witnessed at Port Arthur. If for any cause daylight is considered essential, the darkness may supervene before the squadron is ready to sail, or before the tide serves for return. In any case the ships at anchor are vuhierable to torpedo boats by night and to submarines by day or night. Questions like these are among the practical difficulties of naval warfare and acts of invasion from over-sea, and it is useful that our attention should be directed to them.