108 ANNUAL OF SCIENTIFIC DISCOVERT. 



ence, is very great, since there is no other resistance to this mo- 

 tion except the skin-friction. Mr. Elder proposes to make use of 

 the great momentum which this high velocity of movement will 

 afford for ramming purposes. The whole circular edge of his 

 vessel, which is of a sharp angle in section, represents, so to say, 

 the edge of a circular saw or revolving disk-wheel, and the ac- 

 cumulated momentum of the rotary movement can be used for 

 producing a destructive effect upon the sides of any vessel with 

 which this revolving turret-ship would come into contact. The 

 circular form allows of a very large stowage-room as compared 

 with the ordinary form of ships, and it produces a base of such 

 stability as to allow the erection of a tower of great height in the 

 centre, so as to obtain better facilities for attacking objects on 

 shore. Mr. Elder has carried out some experiments as to the re- 

 sistance to propulsion in a straight line offered by his form of ves- 

 sel compared with the ordinary forms. He made two models 

 representing equal tonnage, one of the '* Black Prince" shape and 

 the other of his spherical form, and the resistance of these two 

 models was measured by an apparatus which afforded a simple 

 mode of comparing the relative proportions of these resistances. 

 The result was only about 10 per cent, in favor of the "Black 

 Prince " model ; and this seems to indicate that the new vessel 

 would" be capable of attaining a fair speed under steam. The 

 advantages offered by this form are of different kinds, the most 

 prominent being a maximum of internal accommodation or stow- 

 age room, with a minimum of exposed surface, a circular or turret- 

 shaped armored side, and an extraordinary facility of manoeuvring 

 in an action ; last, but not least, the total absence of any exposed 

 points of weakness, such as most iron-clads at present possess. — 

 Engineering. 



A NOVEL GUNBOAT. 



A boat named the •* Staunch," built for the Admiralty upon the 

 proposition and plans of Mr. Rendel, has just been tried off the 

 Tyne. A correspondent gives us the following account : "This 

 vessel, though wholly insignificant in appearance and cost, repre- 

 sents some very novel principles. She is only 79 feet long, and 

 26 feet beam ; her draft of water when loaded, 6 feet, and her 

 displacement, 150 tons. She has twin screws driven by 2 pairs 

 of condensing engines of 25 horse-power (nominal) combined, 

 giving her a mean speed of Ih knots. Such being her dimensions 

 and power, it is hard to suppose that she can be in the least de- 

 gree formidable. She carries, however, as heavy a rifled gun as 

 any in the navj^ and to all appearance carries it most efficiently. 

 The gun, a 12^ ton 9-inch Armstrong, is mounted in the fore part 

 of the boat, in a line with the keel, and fires through a bulwark 

 or screen over the bow, wliich is cut down and plated something 

 like that of a monitor. Thus placed, it is easil}' worked in a roll- 

 ing sea, and its change of position by recoil does not appreciabl}'' 

 ali't^ct the trim of the vessel. At the same time, to provide for 



