SCIENTIFIC SUMMAKY. 
431 
secured, the question arose how the power of direction could he acquired, 
that being of the utmost importance in actual warfare. That was ac- 
complished by rotating the balloon to any required position, and then, 
holding it from ^further motion, the rotation was completely under the 
control of the aeronaut. A rudder was the instrument to be used for that 
purpose, a vertical disc fixed in a line with the axis of the propellor. By 
turning the plane of the disc the current of air forced from the fan on the 
rudder caused the whole machine to rotate right or left precisely as the 
rudder of a ship guided the vessel. 
Report on Rainfall . — At the meeting of the British Association in 
Brighton, Mr. G. J. Symons, Secretary of the Rainfall Committee, produced 
the Report of that committee, which was as follows : — a Your committee 
have the honour of reporting that every branch of rainfall work continues in 
efficient working order, and that, notwithstanding the very limited funds at 
our disposal, and the long illness of our secretary during the winter, 
all arrears have been overtaken, and, owing to the completeness of the 
organisation, no hitch or interruption occurred. At the meeting of the 
British Association in Edinburgh very strong representations were made to 
your committee respecting the desirability of establishing additional rain- 
gauge stations in different parts of the highlands, and as your committee 
had long been aware of the necessity which existed for these stations, and, 
moreover, as somewhat larger funds than usual were at their disposal, they 
resolved on taking every means in their power to secure the efficient es- 
tablishment of these stations. In addition to ordinary correspondence, our 
secretary took two special steps to secure the most promising distribution 
of the new gauges. In the first place he wrote to Mr. Buchan, the secretary 
to the Scottish Meteorological Society, acquainted him with the assent of the 
committee, and requested him to state what number of gauges he could 
provide good observers for. On receipt of his reply, ten gauges were sent 
to him, which he was kind enough to distribute as follows : — 1. Springfield, 
Tain, Ross ; 2. Kilmalcolm, Port Glasgow ; 3. Arrochar, Loch Long ; 
4. Strahane, Brodick, Arran; 5. Strathfillan, Perthshire ; 6. Samrose, Arran ; 
7. Kilchoman, Islay ; 8. Port Charlotte, Islay ; 9. Port Ellen, Islay ; 
10. Glenharn Abbey, Mull of Cantire.” 
Powerful Galvanic Batter]). — Mr. Highton described, at the British Asso- 
ciation in Brighton, a new form of battery capable of giving powerful 
effects without fumes or other inconveniences. Negative : Carbon packed 
in a porous cell, with sulphur, peroxide of manganese, and granulated 
carbon, filled up with dilute sulphuric acid ; Positive : zinc in a solution of 
caustic potash or soda. The potential is nearly fifty per cent, higher than 
Groves. One cell will abstract magnesium from its salts. 
ZOOLOGY AND COMPARATIVE ANATOMY. 
Supposed New Marine Animal . — At the British Association Meeting, Dr. 
Sclater, F.R.S., exhibited specimens of bodies having the general external 
shape and appearance of long, thin, tapering, white willow wands, which he 
