MECHANICAL AND USEFUL ARTS. 20 



shall be capable of being submerged in water, so as to either partially 

 or entirely conceal it ; and also in forming the battery thereof, or 

 that pait in which guns are fixed or mounted, so that it shall resist 

 the force of heavy shot or balls. The patentee employs two long 

 hollow cylinders of metal, each formed conical at one end, which 

 constitute the head of the boat or turn-boat; the other and opposite 

 end of one or both of such said cylinders, constituting the stem, is 

 fitted with a screw propeller actuated by suitable machinery inside 

 one or both of such said cylinders ; or one cylinder may be appro- 

 priated for carrying the mechanism to the l engine-boiler and fuel 

 necessary for working the propelling- screw, and the other cylinder 

 may be appropriated for ammunition, and also for the hands or crew 

 of the boat. — Mechanics' Magazine. 



LAND BATTERIES AND GUN-BOATS. 



Mr. J. Arrowsmith has patented a new or improved methodof con- 

 structing Land Batteries and Gun-boats. In the construction of a land 

 battery the patentee rolls bars of iron having a groove running their 

 whole length ou one side, and a projection running their whole length 

 on the other side, the said projection and groove being of nearly the 

 same size. When bars of the kind described are placed upon one 

 another, the grooved sides being all turned in the same direction, 

 the groove on one engages with the projection on the next one. The 

 bars are curved to the required curvature. The walls of the battery- 

 are formed of two thicknesses of the iron described, the outer and 

 inner walls formed by the said iron being separated, and the enclosed 

 space filled with oak. The structure is secured vertically by bolts 

 passing between the walls, and the parts are bound together hori- 

 zontally by girders, which are secured at one end to rings in the 

 middle of the battery, and at the other end to vertical girders fixed 

 in the foundation. The upper of these rings is supported by bars of 

 wrought iron. The roof may be formed of iron similar to that em- 

 ployed for the walls, and the whole structure may be formed inter- 

 nally with oak. The portholes are closed by plates of hammered steel 

 iron sliding between the walls, and supported by a lever and weight, 

 so that by moving a catch the porthole is closed immediately. The 

 guns may be mounted on a turn-table. An underground magazine 

 may be constructed behind the battery, covered with the same sort 

 of iron, and connected with a tunnel leading to the centre of the 

 battery. A steam-engine may be fixed at a distance, having an 

 exhaust cylinder connected by pipes with the batteries, and having a 

 valve to each battery, the said valves being opened as soon as the 

 guns are fired. The smoke is thereby immediately exhausted from 

 the battery. — Mechanics' Magazine. 



MARTIN S ANCHOR. 



A series of experiments has been made in the presence of the 

 Master and Brethren of the Honourable Trinity House, Newcastle- 

 upon-Tyne, and a large number of gentlemen interested in shipping 

 matters, for the purpose of testing tl.e comparative holding-power of 



