NATURAL PHILOSOPHY. 133 



electrical condition of the atmosphere. He lias described in the 

 article on the Electricity of the Atmosphere in Nichol'fl Cyclopcedia, 

 a portable electrometer, and also a mode of collecting electricity by 

 that which he styles the water-dropping system, which would, in his 

 opinion, be easily applicable. The observations might be carried on, 

 first, by ascending to very moderate heights, and then going as high 

 as possible. Dr. Lloyd desires that observations should be made for 

 "the determination of the decrease of the earth's magnetic force with 

 the distance from the surface." The failure of Gay-Lussac to detect 

 any sensible change ought not to deter future observers. His 

 methods were wholly inadequate ; but Dr. Lloyd is of opinion that 

 if attention be confined to the determination of the total force on its 

 vertical component (instead of the horizontal) it would be easy to 

 arrive at satisfactory conclusions. 



Sir David Brewster suggests that further information may be ob- 

 tained as to the polarization of the atmosphere and the heights of the 

 neutral point. And, lastly, Dr. Edward Smith and Professor Sharpey 

 are desirous that experiments should be made as to "the quantitative 

 determination of the products of respiration at different high eleva- 

 tions." Dr. Smith has, as it is well known, been for the last two or 

 three years engaged in experimental inquiries on inspiration ; and he 

 is so satisfied of the value and importance of the investigation, that 

 he is not only willing, but desirous, to make the requisite experi- 

 ments himself. Dr. Smith has furnished directions as to the points 

 to be observed and the mode of observation. 



ATMOTIC SHIP. 



The Hon. W. Bland, N. S. Wales, has proposed to the British 

 Association the construction of a light keel and ship-formed body, 

 buoyed up by an elongated balloon, by two heavy weights guided by 

 a rope slung from stem to stern, so to alter the centre of gravity of 

 the machine as to direct its motion upwards or downwards at 

 pleasure ; and to cause it to move onwards in any assigned direction 

 by the aid of large but light and strong vanes, driven round and 

 acting like the screw-propeller of a ship. 



IMPROVED AIR-PUMP. 



Mr. W. Ladd has described to the British Association an Im- 

 proved Form of Air-Pump for Philosophical Experiments. This 

 pump consisted of an ordinary pump with two barrels to exhaust 

 npidly at the early stage, then a horizontal barrel, worked by a rack 

 and handle ; the piston-rod passing through a stuffing-box and cistern 

 of oil, the top of the barrel forming the side of the cistern, and 

 having a valve opening outwards. In the bottom of this barrel was 

 also a valve, opening outwards, to let out any oil which might, in 

 working, pass the piston. The piston of this third barrel, when it 

 passed a hole in the barrel, communicated the vacuum above its 

 piston through a tube connecting it with the receiver. "When this 

 barrel worked, a cock shut off the two large barrels from the receiver. 

 The author stated that he could exhaust to the T Vth of an inch by 



