Outwardly it was shaped somewhat like a fish, being constructed of a special metal—our joint invention—which we had named "martalium." The metal was composed of aluminium and two other rarer metals which, when combined together, produced a substance almost as light as aluminium, yet many times harder and tougher than case-hardened steel; whilst its surface shone like burnished silver and could never in any circumstances become tarnished or affected by rust.
The ship was ninety-five feet in length, and its diameter twenty feet in the broadest part, tapering off to a point at either end.
With the exception of the steering and balancing fans, there was no machinery whatever visible on the exterior of the vessel. Several windows along each side, together with a few at the top and bottom of the vessel, gave light to the interior, and would allow for observations being made in any direction. These windows were all constructed of a special toughened glass obtained from Vienna, very thick and warranted to withstand the hardest blows. Along each side of the vessel there was an observation platform or gallery on to which the exterior doors opened, and each gallery was provided with a protecting railing.
The interior of the ship was divided into five separate compartments, the rear one being the general living and sleeping room, having observation windows so arranged as to command an outlook in all directions. The next compartment was mainly a store-room, but, like all the others, could be used for observation purposes; next to that was a small compartment intended for a special purpose which will hereafter be apparent; then another containing water storage, apparatus for compressing or rarefying air, as well as machinery for producing the latter chemically.
Lastly, right in the forepart of the vessel was M'Allister's special sanctum, containing the driving, lighting, warming, and steering machinery, but electric buttons and switches were also provided for controlling these in every compartment, so that whichever one we happened to be in we were prepared for all emergencies. Periscopes capable of being turned in all directions also communicated with every compartment, thus we could always see what might be around us.
All the machinery was either electric or magnetic, some of it being very simple; other portions were extremely intricate, but nearly all was the outcome of our joint inventions. Such parts as could not profitably be made by ourselves had been carefully distributed between several firms of founders and engineers, in order that none could have any means of discovering the use to which they were intended to be put. The whole of the shell of the vessel was double, with a packed space between the two skins; and each door opened into a small lobby, having another door on the farther side, to ensure that every part might be kept perfectly air-tight when required.
By the time we had completed a thorough inspection of the vessel and its machinery, and overhauled the stores to make sure that everything requisite was on board, it had become nearly dark, so, moving a switch, M'Allister swung open the great doors at the end of the shed. The vessel was standing upon a low trolley having many wheels running on rails, with a small electric motor beneath it, and, upon M'Allister moving the trolley switch, the whole affair glided smoothly out into the open field. I may as well confess that we owed this trolley and the mode of its working to ideas gained during an inspection of the construction and working of the conduit trams belonging to the London County Council.
When the vessel was out in the open we congratulated ourselves upon its splendid proportions and business-like appearance.
I asked M'Allister whether "he was satisfied with the result of our labours?"