180 Transactions. — MisceltaneouS. 



when it comes to that part of the evokition that is in the same direction as 

 the wind, lower itself, and thus acquire additional velocity. There are, 

 therefore, in this apj^aratus two most potent influences at work to preserve 

 its equilibrium ; — first, its cutting or keel-like property ; and, secondly, its 

 gyroscopic tendency of preserving its plane. This persistency of position, 

 remarkable always in the case of the gyroscope, is rendered still more 

 striking when the wheel is rotated in the air without any visible support. 



A remarkable corollary of this arrangement of the aero-planes is the 

 following : — If the advancing edge of the apparatus is kept slightly tilted 

 uj)wards, we shall be able to utihze the very weight of the machine while in 

 motion as a powerful auxiliary ; for the planes A and B (fig. 4) in their 

 longitudinal sections will be incHned upwards so as to receive a powerful 

 lifting impulse from the induced current of air, while the planes A' and B' 

 will be horizontal in their longitudinal sections and cannot therefore 

 impede the advance. 



Similarly the winds can be utilized even if adverse, as the edge which 

 first catches the wind can be slightly tilted up, so that all the radii A and B, 

 which could be lifted by the wind, can catch it ; while all the other radii A' 

 and B' which would otherwise be depressed will then be in a horizontal and 

 neutral position. It therefore fohows that aU compounded horizontal air 

 currents also admit of being transformed to a great extent into a buoyant 

 force. 



Art. XVII. — On Floods in Lake Districts and Flooded Bivers in general, icitli 

 Methods adopted for their Prevention and Control. By H. P. Higginson, 

 Mem. Inst. C.E. 



Plate XIV. 

 [Read before the Wellington Philosophical Society, 2nd February, 1878.] 

 WhUe at Queenstown, on Lake Wakati^ou, during last November, a 

 heavy rainfall was experienced, which, together with the melted snow on the 

 main ranges, caused a rapid rise in the level of the lake. On Saturday 

 morning, the 17th November, the rain-gauge at Queenstown registered -66 

 of an inch, which fell during the previous night ; and on Sunday morning 

 an additional 1-61, making 2-27 inches during forty-eight hours. The rain 

 being from the north-west melted the snow with great rapidity, causing 

 an immense rush of water into the lake, the level of which rose over two feet 

 in the two days. 



