4. M. Villaine, inventor of a special design for a submarine boat, intended to be employed in gold-mining under water, was present by invitation, and on his behalf Mr. Nuttall explained the design.

It was represented that an iron boat on this principle, 26ft. long by 7ft. in diameter, is capable of containing three men at work for six hours at the bottom, without communicating at the surface. Provision is made for propelling the boat under water. The interior of the boat is divided into compartments, namely, a ballast chamber, a place for working in, airtight compartments containing air compressed to six atmospheres, and a space into which water is admitted to sink the boat, the water being afterwards used to wash the metallic ore, there being a sluice 30ft. long in the boat. There is also an open space for allowing communication between the two ends of the vessel, and there are pipes and cocks for regulating the air, and chemical means are taken for renovating it. Provision is made for those inside to move the boat ahead or astern on the bottom, for maintaining the equilibrium of the boat, and for fixing it upon an angle of 45° or 50° if required. The mode of working it is as follows:—The boat being brought to the scene of operations, those intending to descend get into her through a man-hole. When a sufficient quantity of air has been accumulated in the reservoirs, the man-hole and air-funnels are hermetically closed, and sufficient water is then admitted to sink the boat. Once on the bottom, the compressed air is allowed to rush into the working chamber, upon which the bottom of the boat, an iron door of eight superficial feet, is opened, and work is commenced. The vessel is again brought to the surface by discharging the water taken in.