1877: The Hemi-Plunger Ship by Monsieur Donato Tomassi

Ran into this 1877 ship designed by a certain M. Donato Tomassi. It does not sound like this ship was ever made, but then again, do we really know? Here is a short description of this 19th century wonder.

The Hemi-Plunger

The novel form of vessel, to which the above odd name has been given by its inventor, M. Donato Tommasi, of Paris, France, is a combination of a boat wholly submerged with a raft: a connecting link, to borrow the naturalist's expression, between the submerged torpedo boat and the monitor. The advantages which are expected to be realized from this hybrid craft, the inventor describes as follows: "It is evident that a vessel, plunged several yards below the surface of the sea, is no longer influenced by wind or wave. Let the sea be agitated, let there be the most violent tempest, yet the boat which navigates under water will never be wrecked, for the same reason that a fish cannot be drowned.
  • What a beautiful vision, that of traversing the ocean, as a balloon floats through the air, with the same tranquility, without shocks, without the insupportable rolling and pitching!" etc. The construction of the invention introduced in this glowing manner will be understood from Figs. 1 and 2.
Figure 1
  • G - the rudder.
  • B - the platform.
  • H - the propeller.
  • I - the tube through which sea water passes to the pump.
  • A - the plunger cylinder.
  • E - two hollow columns. They serve as shoots down which merchandise is lowered to the compartments. Their upper ends are received in two immense inverted cups attached to the bottom of B. Through these cups pass large screws, which confine the columns so that, by removing the connection, the whole submarine apparatus may in case of necessity be freed from the upper works.
  • F = metallic plates (attached to E) designed to to diminish friction through the water.
Figure 2
  • A - the plunger cylinder, shown with its side broken away
  • E - two hollow columns.
  • F = metallic plates (attached to E) designed to to diminish friction through the water
  • C - the smokestack
  • M - compartments in which water may be admitted to increase the weight, and hence the depth of flotation of the plunger, the same being filled or emptied by the pump
  • P&N - the hold for merchandise, partitioned off from the boiler room as shown
Figure 3

On each side of the platform, B, which is of elliptical figure, is a large float, seen in Fig. 3, which, by means of racks and gearing, may be raised or lowered at will. Usually these floats are carried at a height of a yard above the water. In calm weather, this distance is increased, and in storms it is diminished, the object of the floats being to keep the whole vessel on an even plane, and to prevent too violent oscillations. In order to facilitate navigation in shallow water, the columns, E, may be made telescopic, and operated by hydraulic apparatus, so that they may be shortened at will. Any form of engine or propeller may be used.

Besides the advantage of the vessel being unaffected by waves, since its submerged portion travels far below them, the inventor claims that it will meet less resistance from the water than would a vessel of corresponding volume sailing on the surface. It will make faster progress, because it has no waves to mount and descend; and hence it always travels in a nearly right line. The screw being submerged at a great depth will not tend to turn the vessel from her straight path. The platform being easily detachable may serve as a raft in case of injury to the submarine boat. For fast travel, on lakes, rivers, and shallow water generally, M. Tommasi proposes to support his platform on two floats which rest on the surface of the water. No weight, therefore, is thrown on the submarine vessel, which need be constructed with only just enough buoyancy to sustain itself and its engine. In this way, the upper craft has no engine or other load than its cargo; and as it merely rests upon the surface, the inventor thinks that it will skim over the same like an ice boat on ice.

In War: For war purposes, the hemi-plunger is especially adapted, because the vulnerable portions, engines, boiler, rudder, etc., are wholly out of the reach of shot. Guns are mounted on the platform, which thus becomes a circular or elliptical turret, just above the water when the vessel is in fighting trim. Instead of steel armor, M. Tommasi has a new invention which he calls hydro-metallic plating. He reserves the details of this for future publication; but generally the armor consists of tubes in which liquid is forced under a pressure equivalent to the resistance, say, of forged steel. He thinks this will oppose shot as effectually as the solid metal, and will have the additional advantage of superior lightness.

Sources and Links:

KD: What do we really have here? Are we supposed to believe that some unknown dude named Donato Tomassi, single-handedly designed a merchandise transporting submarine with a detachable platform? The one that can be easily turned into a warship? In 1877?

What do we know about this Monsieur Donato Tomassi? From the article we know that he was an inventor from Paris.
  • When was he born?
  • Where did he study?
  • Who did he work for?
  • When did he die?
Googling around suggested that he had something to do with chemistry:
  • French: La note de M. Donato Tomassi, présentée lors de la séance de mars dernier et concernant l'action du magnésium sur les composés minéraux et organiques, sera déposée aux archives, conformément à l'avis des commissaires, MM. Donny et Stas.
  • English: The note by Mr. Donato Tomassi, presented at the meeting last March and concerning the action of magnesium on mineral and organic compounds, will be deposited in the archives, in accordance with the opinion of the commissioners, MM. Donny and Stas.
  • 1874 Source
A different 1874 source corroborated our Monsieur Donato Tomassi being (at least) a chemist.


Further Googling showed that he was possibly an electrician and a civil engineer. It's all in French. Here is a couple of links and a portion of google-translated text:
  • Each electrode of the D. Tommasi accumulator is composed of a tube of hardened lead or of any insulating material (ebonite, celluloid, porcelain, etc.), closed by an insulating plate, and a metal rod in hardened lead engaged in this bottom and serving as conductor. The tube may be of cylindrical, square or rectangular shape; that of the conductive rod naturally varies according to these different forms.
Additionally we could say that Donato Tommassi studied magnetism. OK, so the guy appears to have existed and was smart, but could he design a ship like this?

Anyways, for the time being I'm maintaining my opinion that they were trying to re-create the inherited tech of the previous spin of civilization. May be this guy was one of the survivors, I do not know.

These are my thoughts. What are yours? Do you think they got to building an actual ship?