120 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 27 



merely safety appliances to insure its recovery from the water. The reel con- 

 sists of a light spool on which a fine cord is wound, one end of which is attached 

 to a light float that detaches itself and lies upon the surface of the water when 

 the machine sinks, while the other end is fastened to the spool that goes down 

 with the aerodrome. The " float " is a light copper vessel with conical ends 

 which is firmly fastened to the midrod, and which is intended to so lower the 

 specific gravity of the whole machine that it will not sink. The cylindrical por- 

 tion of this float has a length of -Jot) mm. and a diameter of 170 mm., one cone 

 having a length of 65 mm. and the other and front one a length of 140 mm., 

 which makes the total length of the float 375 mm. It is made of very thin cop- 

 per, and served in the successful trials not only as a float to sustain the machine 

 on the surface of the water, hut also as a weight by which the center of grav- 

 ity was so adjusted that flight was possible. 



The counter records the number of revolutions of the propellers after 

 launching. It is a small dial counter, reading to 10,000, with a special attach- 

 ment which prevents any record being made of the revolutions of the propellers, 

 until the actual moment of launching, when a piece on the launching apparatus 

 throws the counter in gear at the instant that the aerodrome leaps into the air. 



Description of Aerodrome No. 6 



Aerodrome No. (i, it will be remembered, was the outgrowth of a number of 

 changes made in No. 4 during the fall of 1895 and the early part of 1896. In 

 this reconstruction the aim was to lighten the whole machine on account of the 

 smaller engines used on No. 6, and to arrive at better conditions as regards sta- 

 bility than existed in either No. 4 or No. 5. The modifications from No. 4 were 

 so radical and the differences that exist between Nos. 5 and 6 are so consider- 

 able as to demand careful attention. 



As regards general appearance the frame of Aerodrome No. 6 resembles 

 that of No. 5 in consisting of a single continuous midrod of steel tubing, 20 mm. 

 in diameter, 0.5 mm. thick, immediately beneath which the hull containing the ma- 

 chinery is situated. In reconstructing the framework after the tests in Janu- 

 ary, L896, had shown it to be dangerously weak, especially against torsion, it was 

 decided to make the hull only strong enough to carry its contents and to attach 

 it to the stronger midrod in such a way Hint all torsional strains would be taken 

 up by it, whereas in No. 5 the hull structure must bear a large proportion of 

 such strains. It was therefore built throughout of 8-mm. tubing, 0.3mm. thick, 

 and was rigidly attached to the midrod by braces at the front and rear, and also 

 at the cross frame. The hull was also made narrower (except at the rear, where 

 it was widened to contain the boiler) and shorter than the hull of No. 5 — an ad- 

 \ antageous change made possible by the fact that the engines were not contained 

 in the hull, but mounted on the transverse frame. 



