ON THE 74oz. COMPRESSED-AIR FLYING-MACHINE. 253' 



decided opinion to the same effect. Of course, the theory that the 

 Dravidians and the blacks of Australia and Melanesia are inti- 

 mately related was not new ; for, even twenty years before that, 

 Bishop Caldwell had drawn attention to the similarity in structure 

 between the Australian pronouns and those of what he calls the 

 Scythian group, which includes the Dravidian. But I held then, 

 and still hold, the belief that our black race came originally from 

 Babylonian lands in two streams, at different times, and passed 

 through India, resting there for a time before it reached Australia. 

 Of these two streams, the first, I imagine, was of tolerably pure 

 Hamite blood ; the next much mixed. I can give reasons for 

 holding this opinion ; perhaps I may some day ask you to listen 

 to them. 



ON THE 74oz, COMPRESSED-AIR FLYING-MACHINE. 



By Lawrence Hargrave. 



[With Four Diagrams.] 



[Read before the Royal Society, N.S.W., December 3, 1890.'] 



A larger compressed-air flying-machine than that described on 

 June 4 last, has made two flights that are worth recording here. 

 They are numbered, in the writer's memoranda, Trials 5 and 6 of 

 No. 5 Tin cylinder vibrating engine. No. 4 Tin engine with a 

 receiver capacity equal to that of No. 5, was fitted with the 

 expansion gear that was exhibited in this room, but its irregular 

 working and intermittent action on the piston soon showed it to 

 be unsuitable for such small models. A new Richard's Indicator 

 revealed the fact that the air pipe and ports were too small. 



Another form of reducing valve was tried and from the chrono- 

 grams taken it was inferred that the cylinder pressure was uniform 

 for a number of strokes. The chronographic apparatus was 

 remodelled and Diagram 4 shows its simplicity and handiness. 

 Three simultaneous records are made ; the time in seconds, the 



