AEKONAUTICS. 61 



The soaring kite with the double propeller rolls very sharply; 

 this is thought to be due to the centre of gravity being too low. 

 The rod is now clamped to the steel wires joining the two parts of 

 the propeller, in such a way that it can be adjusted vertically. 



As it seems impossible to arrange for the members to see these 

 particular experiments, it is thought that an accurate drawing of 

 the model is amply sufficient to enable others to reproduce and 

 extend the elementary observations here recorded. 



The principle points that require investigating, are : — 



1. How much the after edge of the propeller can be cut away 

 without impairing its efficiency ? 



2. What is the diameter of vortex that is best for general use? 



3. How many propellers can be advantageously superposed 1 



4. The proper relation between the propeller area and the kite 

 area. 



5. The shortest rod that will keep the longitudinal equilibrium 

 stable. 



6. What is the supporting power of the propeller when used 

 for gliding, as compared with that of the gliding machines now 

 used? 



7. Can the vortex be produced by a motor in calm air so as to 

 be more economical than the thrust of a screw? 



8. To make an instrument to show simultaneously what pressure 

 there is at every part of the concave and convex surfaces of the 

 propeller. 



These alone form a large volume of work for one pair of hands 

 to endeavour to accomplish, and it appears regrettable that Aus- 

 tralians should leave to Americans and others the tardy adoption 

 of the views circulated by this Society. 



A steam screw motor Figs. 3 and 4, which is intended to develop 

 five or six horse power has taken up much time, but as yet it will 

 not work in a reliable manner. It is of course quite a secondary 

 consideration while the soaring kites are developing. The water 



