180 Transactions.— Miscellaneous. 
when it comes to that part of the evolution that is in the same direction as 
the wind, lower itself, and thus acquire additional velocity. There are, 
therefore, in this apparatus 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 
upwards, we shall be able to utilize the very weight of the machine while in 
motion as a powerful auxiliary; for the planes 4 and B (fig. 4) in their 
longitudinal sections will be inclined upwards so as to receive a powerful 
lifting impulse from the induced current of air, while the planes A’ and B’ 
wil 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 4 and B, 
which eould 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 follows that all compounded horizontal air 
currents also admit of being transformed to a great extent into a buoyant 
force. 
Art. XVIL.— On Floods in Lake Districts and Flooded Rivers in general, with 
Methods adopted for their Prevention and Control. By H. P. Hicerson, 
Mem. Inst. C.E. 
: Plate XIV. 
[Read before the Wellington Philosophical Society, 2nd February, 1878.] 
While at Queenstown, on Lake Wakatipu, 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. 
