56 LAWRENCE HARGRAVE. 



the body is best removed as it only serves to conduct the air, the 

 inertia of which has been overcome by the weight of the forward 

 part of the machine, to the tail. Whereas if the middle of the 

 body plane has been cut out the used air escapes upwards and the 

 tail has a better chance of getting comparatively solid air to float 

 on. The neglect of previous knowledge gained partly arose from 

 reasoning that in calculating the area in advance of the centre of 

 gravity the dividing line should be taken through the centre of 

 gravity of the machine when wound up ready to fly, instead of 

 through the mean centre of gravity; as in the india rubber driven 

 machines it is moving forward as the bands contract. 



Another experiment was made that bears on this point of the 

 continuity of surface. A stick and paper model for the cross bow 

 had two surfaces, 10 inch by 10 inch, in the same plane, separated 

 by a distance of 15 inches, with the centre of gravity in the middle, 

 that is 7 *5 inches from either plane. This showed a slight inclin- 

 ation to rise forward, but equilibrium was established by moving 

 the centre of gravity only '72 inch from the geometrical centre. 



Every effort has been made to render this matter intelligible, 

 and no pains have been spared in making the drawings perfect ; 

 but some apology is due to the members for their inferior repro- 

 ductions in the last paper " Flying-machine Memoranda," which 

 were not submitted to the author for approval. 



It is well known that publishing the results of experiments as 

 they progress is not a course that most inventors would pursue, 

 but the whole subject is thought to be so far-reaching in its effect, 

 and the varieties of practicable flying-machines so numerous, that 

 any attempt to secure a monopoly of the profits accruing from 

 their construction would be a mean and selfish proceeding, and 

 totally unworthy of consideration. The writer feels assured 

 that if he should ever make flying-machines for sale his productions 

 will be as well appreciated as any others ; and that the endeavour 

 to strangle the work of others by patenting would only result in 

 real progress being hampered by conflicting monetary interests 

 and much ill feeling.* 



The use of paper as a material for the required surfaces is still 

 recommended, damages are then so easily repaired ; there is no 

 need to take much trouble in stretching it at first as after the 



* The writer thinks the act of invention to be a sort of inspiration, 

 and a pleasure that the individual does not seek to be rewarded for 

 undergoing- ; it is followed by a greedy sensation or wish to obtain money 

 from others without giving an equivalent. This results in the develop- 

 ment of the invention by the ordinary work of drawing-board drudges 

 and laboratory experimenters who are not generally permitted to share in 

 the profits of a patent. Inventors will always invent, they cannot help it, 

 .and you cannot stop them ; and a patentee is nothing but a legal robber. 



