The _Gemini_ twin steamer, invented by Mr. Peter Borrie, was a double-hulled boat, launched in the summer of 1850. The keels and stems were not placed in the centre of the hulls but towards the inside of them, thus making the water-lines very fine on the inside. This was intended to diminish the tendency of the water to rise between the hulls. The inner bilges were much fuller than the outer ones, the idea being to afford a greater degree of buoyancy on the inside, in order to support the weight of the deck. The steamer was 157¹⁄₂ feet long over all, and 26¹⁄₂ feet broad on deck. Each hull was 8¹⁄₂ feet broad, with a space 9¹⁄₂ feet between them. The frames were of angle iron, and the keels were formed by carrying the plates downwards, so as to form channels for the bilge-water inside the hulls. This arrangement was intended for river craft of this type, but for sea-going vessels drawing more water the inventor planned keels of iron bars, with the garboard-strakes riveted upon them in the customary way. The plating was not carried to the top of the frames on the inner side of the hulls, except at the space in the middle for the paddle-wheel, but was carried up to the deck, thus forming an arch between the two hulls, which were bound together with stays. The hulls were divided into water-tight compartments. The vessel was two-ended and could travel in either direction without turning. There was a rudder at each end, placed in the centre of the opening between the two hulls. It was constructed somewhat in the manner of the balanced rudder of later years, as it was affixed, to a vertical shaft in such a way that it was divided into two unequal parts, and when left free would accommodate itself to the vessel’s motion. The steamer was estimated to carry from 800 to 1000 passengers.