The Cylender or incompressible part of this Vessel being 6 feet diameter and 24 feet long will have an Area of 672 cube feet on allowing a Man to consume the Oxygene of 20 Cubic feet in an hour it would be suffecient for one Man for 33 hours or for 6 men for 5 hours or should each Man consume the oxygene of only 15 cube feet in an hour and which is the usual estimate, there would be suffecient for 6 men for 7 hours or should a greater supply of air be necessary for any particular operation it may be done as in the following sketch [Illustration] _A_ is a cast Iron or copper box one cube yard or 27 cube feet. Into this 20 atmospheres may be compressed by proper pumps. _B_ is a measure of half a cube foot. _C_. _D_ two cocks, _C_ being shut, _D_ is opened and the measure _B_ filled. _D_ is then Shut and _C_ opened which lets the measure of air circulate in the Vessel, the 20 atmospheres compressed in in this reservoir would equal 540 cube feet of common air and suffice for the 6 men for 5 hours more and thus the 6 men might continue under water 11 hours in such case were they in a harbour or surrounded by a fleet they could continue under water all day and mounting with their air pipe out of water in the night renew the air for the following day, but this is contemplating an extreme case, a Vessel which can stay 4 hours under water can move 8 miles in that time where the tide is two miles an hour and could get out of any open harbour Such as Brest, Cadiz & [Illustration: PLATE THE TWELFTH ] * * * * * On the weight of the Cylender and its Buoyancy Suppose it cast one inch thick on calculating its cube inches and allowing 4 cube inches of brass to a pound it would Weigh about 8 tons. Its volume of water or 672 cube feet would weigh upwards of 16 tons, hence such a cylender hermetically cloased would float 8 tons lighter than Water CHAPTER VI THE BRITISH CONTRACT Size of the “Drawings and Descriptions.” Pseudonyms. Proposals. Contract with the British government. Was Fulton false to his principles in supporting Great Britain against France? His financial position under the contract.