The Lieutenant demurred at the assertion, while the Sub was equally emphatic. "Don't argue about it!" exclaimed the Hon. Derek. "The best way you can settle the matter is to toss for it." A florin glittered as it spun in the rays of the electric light. "Heads!" declared Macquare. "It's your go, laddie, and good luck!" In common with other submarines of the "R" Class, Stockdale's command was provided with a means of enabling divers to leave the interior of the vessel while submerged. One of the sub-compartments was fitted with two water-tight doors, one of which communicated with the interior; the other, in the vessel's side, gave access to the outside. Without loss of time the Sub called for two volunteers. Of the submarine's complement twelve men had "proficiency pay" as seamen-divers, and every one of the twelve volunteered for the hazardous task. "I'll take Cassidy and Payne," decided Fordyce. "They are most reliable men, and both unmarried. If we are not back in an hour, sir, don't wait if you have a chance. We'll do our best." "And good luck!" exclaimed the Lieutenant-Commander. It was the naval way of bidding farewell to a comrade about to undertake a risky enterprise--a pithy expression conveying a wealth of possibilities of thought. Assisted by willing helpers, the Sub and the two seamen donned their diving-dresses. These were of the "self-contained" type, in which the cumbersome life-line and air-tube are dispensed with. The dresses were of "armoured" rubber and canvas, specially contrived to withstand high pressures. The copper helmet was fitted with three large scuttles, so that the wearer could see what was going on on either side by merely turning his head, and thus doing away with the necessity of having to keep the desired object in view directly in front. At the back of the helmet was a flexible metal tube supplying chemically-treated air from a reservoir to the wearer. The reservoir was strapped to the small of the back, if such an expression can be applied to an inflated diving-dress. Immediately above the breathing-apparatus container was another contrivance of strong elastic material, capable of being expanded to double the size of a football. Normally it lay flat and compact against the diver's shoulders. Strapped across the chest, immediately below the leaden weight attached to the collar of the helmet, was a strong copper receptacle connected with the deflated bag on the diver's back, and fitted with a stopcock and a small but powerful suction-pump. This contrivance took the place of the life-line in the older type of dress; for, should a man wish to rise from the bottom of the sea, all he had to do was to release the compressed air from the copper container into the expanding bag, until the buoyancy of the latter overcame the weight of the diver's equipment.