(e) A ship, if damaged, would be five hundred miles from any friendly dock and seven hundred miles from any friendly arsenal. Replenishments of ammunition, fuel, food and water would have to be brought to the attacking fleet across these distances of sea, past many islands and through one or two channels well suited to be the lurking grounds for enemy submarines. On the other hand, there was the possibility that the heavy naval guns would make the field works untenable, that observers in aeroplanes and seaplanes would locate, range and observe the fire upon the hidden batteries, that thus the mine sweepers would be able to clear a passage up the Straits without undue interruption, and complete the task demanded of them without military assistance. Before operations could be begun by the Allied fleets it was necessary to secure some harbour, as close as possible to the Straits, to serve as what is called an advanced or subsidiary base, where large stores of necessaries, such as fuel and munitions, could be accumulated for future use by the ships engaged. The port of Mudros, in Lemnos, was selected as this subsidiary base. This great natural harbour, measuring some two by three miles across, provides good holding ground in from five to seven fathoms of water for half the ships in the world. Two islands in the fairway divide the entrance into three passages, and make it more easy for the naval officers to defend the approaches. It is a safe harbour for ocean-going ships in all weathers, but with northerly or southerly gales, such as spring up very rapidly there in the changeable seasons of the year and blow with great violence for some hours at a time, the port is much wind-swept and the sea makes it dangerous for boats to lie alongside ships. Mudros itself, the town from which the port is named, is a small collection of wretched houses inhabited by Levantines, who live by fishery, petty commerce, and a few olive gardens and vineyards. It has a cathedral or largish church, and a small wooden pier, without appliances, for the use of the native boatmen. The town lies to the east of the harbour, on some rising ground or sand which stands up a little higher than the surrounding country. Behind it, rather more than a mile away, are barren hills of some 800 or 900 feet. The port is ringed in with these hills; it looks like a great extinct crater flooded by the sea. Over the hills in fair weather the peaks of Samothrace can be seen. When the spring flowers have withered the island is of the colour of a lion's skin. Its only beauty then is that of changing light.