FOR A NEW FORM OF LIGHTSHIP^ ETC. 159 



whicli is represented in the accompanying drawing is of 

 wrought iron ; the tube or stem at its upper end is of a 

 diameter sufficient only to admit the body of a man easily, 

 and at its lower end the diameter is doubled to give in- 

 creased strength. The lantern, with light-room beneath it, 

 and gallery attached, terminates the superior end of the 

 tube, while its inferior extremity is riveted on to the 

 dwelling place of the attendants, which is the frustrum of 

 an inverted cone with convex ends. To the base of the 

 cone and in its plane a wide annular flange is securely 

 stayed, and the vessel is weighted by means of pigs of 

 iron stowed in the hold and a cast iron sphere suspended 

 beneath, so that the dwelling apartment is sunk beneath 

 the surface of the water, and beyond the reach of the 

 action of the waves. The exact form and dimensions 

 will depend in part on the depth of the water, the range 

 of light required, and the exposure of the situation. The 

 following are the chief particulars of such a lightship as is 

 represented in the diagram : 



With the exception of the brass- work and glass of the 

 lanterns, the vessel is constructed entirely of wrought iron. 

 The plates* of the submerged part and those within reach 

 of the waves are very strong, but thinner ones are used for 

 the upper part. The upper lantern is five and a half feet 

 in diameter, the light-room six feet in diameter and six 

 and a half feet high. The whole structure is one hundred 

 and twenty-seven feet in length, two-thirds of which are 

 exposed, and one-third submerged. The tube, two feet 

 and a half at the top, increases to five feet in diameter 

 at the water-line, and is seven feet when connected with 

 the dwelling. The tube, which is divided vertically into 

 two shafts of unequal size, furnishes means for efficient 

 ventilation. An iron ladder is secured in the larger or 

 downcast shaft, while the smaller or upcast shaft encloses 

 the smoke flue. The dwelling apartment consists of a cir- 



