104 ANNUAL OF SCIENTIFIC DISCOVERY. 



retire to Garzcgna when his vacation commenced, and to make incessant 

 observations on atmospheric electricity, night and day, sleeping; in the room 

 with his electrometer, in a lofty position, from which he could watch the sky 

 all round, limited by the Alpine range on one side, and the great plain of 

 Piedmont on the other. Unless relays of observers can be got to follow his 

 example, and to take advantage of the more accurate instruments supplied 

 by advanced electric science, a self-recording apparatus must be applied to 

 provide the data required for obtaining knowledge in this most interesting 

 field of nature. The author pointed out certain simple and easily-executed 

 modifications of working electrometers, which were on the table before him, 

 to render them self-recording. He also explained a new collecting appa- 

 ratus for atmospheric electricity, consisting of an insulated vessel of water, 

 discharging its contents in a fine stream from a pointed tube. This stream 

 carries away electricity as long as any exists on its surface, where it breaks 

 into drops. The immediate object of this arrangement is to maintain the 

 whole insulated conductor, including the portion of the electrometer con- 

 nected with it and the connecting wire, in the condition of no absolute 

 charge ; that is to say, with as much positive electricity on one side of a 

 neutral line as of negative on the other. Hence the position of the discharg- 

 ing nozzle must be such that the point where the stream breaks into drops is 

 in what would be the neutral line of the conductor, if first perfectly dis- 

 charged under temporary cover, and then exposed in its permanent open 

 position, in which it will become inductively electrified by the aerial electro- 

 motive force. If the insulation is maintained in perfection, the dropping will 

 not be called on for any electrical effect, and sudden or slow atmospheric 

 changes will all instantaneously and perfectly induce their corresponding 

 variations in the conductor, and give their appropriate indications to the 

 electrometer. The necessary imperfection of the actual insulation, which 

 tends to bring the neutral line downwards or inwards, or the contrary effects 

 of aerial convection, which, when the insulation is good, generally preponder- 

 ate, and which, in some conditions of the atmosphere, especially during 

 heavy wind and rain, are often very large, are corrected by the tendency of 

 the dropping to maintain the neutral line in the one definite position. The 

 objects to be attained by simultaneous observations in different localities 

 alluded to were: 1. To fix the constant for any observatory, by which its 

 observations are reduced to absolute measure of electro-motive force per foot 

 of air. 2. To investigate the distribution of electricity in the air itself 

 whether on visible clouds or in clear air by a species of electrical trigo- 

 nometry, of which the general principles were slightly indicated. A port- 

 able electrometer, adapted for balloon and mountain observations, with a 

 burning match, regulated by a spring so as to give a cone of fire in the open 

 air, in a definite position with reference to the instrument, was exhibited. 

 It is easily carried, with or without the aid of a shoulder-strap, and can be 

 used by the observer standing up, and simply holding the entire apparatus in 

 his hands, without a stand or rest of any kind. Its indications distinguish 

 positive from negative, and- are reducible to absolute measure on the spot. 

 The author gave the result of a determination which he had made, with 

 the assistance of Mr. Joule, on the Links, a piece of level ground near the 

 sea, beside the city of Aberdeen, 8 A.M. on the preceding day (September 

 14), under a cloudless sky, and with a light northwest wind blowing, with 

 the insulating stand of the collecting part of the apparatus buried in the 

 ground, and the electrometer removed to a distance of five or six yards, and 



