140 



REPORT — 1844. 



account of them will perhaps be a subject for report when the observations 

 made with them are i-ecorded. 



A sort of minute Leyden jar, mounted in the chloride as above, retained a 

 remainder of a low charge 15 days, but it lowered the tension of the con- 

 ductor from 2 to 5 degrees, and more accordingly as the electricity of the air 

 was frequent or slotv. 



6. Experiments on Induction, &c. by Atmospheric Electricity. 



Professor Wheatstone has several times repeated, in a very striking and 

 pleasing manner, the experiments of Herr Erman and M. Peltier, &c. rela- 

 tive to this subject, and such kinds of operations have never failed when 

 tried upon the flat roof, and in fine or appropriate weather. 



The electroscope used was of Bennet's kind but square, and the conductor 

 about 15 inches high, with a hollow copper ball on its summit of 3 inches dia- 

 meter. 



I have also occasionally substituted a " solfcmello" (following Volta) for the 

 ball, in order to exhibit the difference between electrisation by induction and 

 absorption. 



In the fiirst case, after the electrometer has been touched in its high position, 

 the leaves do not (of course) diverge again until absorption takes place, after 

 the lapse of a considerable length of time, and when the insulation is ex- 

 tremely good. In the second case they instantly begin to diverge, and attain 

 to a greater divergence than by induction, all else being equal. 



Small gold leaves being very liable to derangement, &c,, and being less 

 applicable to a scale-measurement than straws, I have constructed a pair of 

 voltaic electrometers for these experiments (and others requiring portability), 

 similar to those of figs. 4 and 5, excepting that the cover T is screwed upon 

 the case, and a very light conical-jointed tube about 3 feet 3 inches long can 

 be screwed upon the wire, which supports the straws, and either a hollow light 

 ball or a solfanello can be fixed on the top of it. The glass tube S is longer 



