would be necessary to build a still stronger cabin, that is to say, heavier 

 (and in consequence with a bigger float), or one of a smaller diameter. 



THE COMPLETED CABIN 



Our cabin has the same dimensions as that of the FNRS 2 and the 

 FNRS s : internal diameter, 6 ft. of in. (2 m.) ; thickness of the wall, 

 3'543 in. (9 cm.), increased to 5-9 in. (15 cm.) around the porthole and 

 the door; diameter of the porthole seating, 3-94 in. (10 cm.) on the 

 inside and 15*75 in. (40 cm.) on the outside. The window is a cone of 

 plexiglas of the exact dimensions of this aperture. The manhole has 

 a diameter of 16-9 in. (43 cm.) on the inside and gradually increases 

 to 21-65 in. (55 cm.) on the outside, where it is tightly closed by a steel 

 door in the form of a truncated cone. In the centre of this door is 

 placed the second porthole in plexiglas, identical with the other. 1 



Fig. 3 shows a section of the cabin (without the joints). Here are 

 seen two hemispheres ; in the centre of one is placed the chief observa- 

 tion porthole, in the centre of the other the door with the second port- 

 hole. The axis of symmetry passing through the centre of these two 

 openings makes an angle of 18° with the horizontal. The door opens 

 obliquely towards the top in the antechamber and the principal port- 

 hole thus looks obliquely downwards. Twelve holes bored in the wall 

 around the main porthole permit the passage of the cables and tubes, 

 which will be described in due course. 



THE DOOR 



The door, the dimensions of which are given above, weighs 352 lb. 

 and its operation presents something of a problem. In the beginning I 

 had envisaged a sliding system with hydraulic control, rather like a 

 London tube door. This system was rather too complicated for us. 

 Afterwards the engineer, Mr. Flagiello, suggested a hinge with a 

 horizontal axis allowing the door to be opened downwards. As I was 

 still not altogether satisfied with this idea, I decided to place the hinge 

 laterally, its axis making an angle of 18° with the vertical. With this 

 arrangement the door opens to the side, obstructs the passage less than 

 if it opens downwards and is operated more easily. I had been afraid 

 at the beginning that the hinge would prevent the door when closed 

 from settling with the necessary precision into its conic seating, but 



1 These portholes are identical with those of the FNRS 2 and the FNRS 3. 

 In the Appendix details will be found of the working out of the design. 



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