124 REPORT — 1844. 



C C C is a strap of copper pressed under the washers at Z Z, and in good 

 conducting contact with the strap of lead C (fig. 2)*. 



The Henley electrometer (figs 7 and 8) is also constructed in conformity 

 with Volta's improvements f. 



The brass piece A is cylindrical below and flat above ; on each of the 

 smaller sides of the upper part is affixed a semicircular plate of ivory BB ; 

 through these the shanks of two little balls (CC) are screwed, which are drilled 

 to receive fine steel pivots, carrying a little ball, into which the index (or 

 pendulum) D is inserted : D terminates with a pith-ball E. The scale is 

 divided into degrees of the circle : each degree should correspond with 

 degrees of the Volta No. 2, and consequently with degrees of the No. 1 (or 

 standard) ; every part is carefully rounded and smoothed. 



It is supported by a piece of tube F passing through a clamping-ball and 

 plug G, and that ball is affixed to one of the cross arms Q (vide fig. 3); the zero 

 of the scale can be therefore accurately adjusted to coincide veith the pen- 

 dulum when unelectrified, and this can be made to rise in a plane cutting the 

 axis of the conductor, &c. with the back of the instrument A turned towards 

 the conductor, &c. ; these are two essential conditions. 



This electrometer has seldom been observed until the Volta No. 2 had risen 

 beyond 90" (in terms of the first, i.e. 18 lines x 5); and since the uncertainty 

 and difficulty of measuring the higher tensions increase in a rapid ratio with 

 the increments of tension, owing to unavoidable and sometimes almost im- 

 perceptible " spirtings" and particularly to the falling of rain from the dish 

 or funnel N (fig. 2), proportionably less confidence must, of course, be placed 

 in our notations of such tensions by means of this instrument J. 



It also requires, according to Volta, De Luc, &c., small corrections for all 

 degrees below the 15th and above the 3.5th, which have not been made in 

 our Journal §. 



A galvanometer by M. Gourjon, S (fig. 2), which Professor Wheatstone 

 has placed on our table, will, I hope, prove the nucleus of a very valuable 

 assemblage of new facts. In low intensities we have not yet been able to 

 apply this instrument successfully, but in higher tensions the needles have been 

 strongly affected. 



The galvanometer in some improved form should perhaps supply that great 

 desideratum in atmospheric electricity, a means of noting the dynamic effects 

 which are perhaps coincident, if not identical, with the property discovered 

 by Beccaria, and called by him " frequency," a property of great importance 

 possibly considered in relation with the various opinions and theories which 

 have been or still are entertained concerning the natural agency of atmo- 

 spheric electricity, in vegetation, animal life, the magnetism of the earth, 

 the aurora, &c. 



Should we be enabled to prosecute these inquiries in the manner which 

 the Professor lias most ingeniously contemplated, or by means of a much 

 more extensive collecting apparatus than the single lamp, &c., I hope that 

 we shall do some good in this way. 



* The Cavalier' Aniici has (on visiting the observatory), in a very kind and flattering man- 

 ner, expressed his conviction that if Volta (his friend) could now see these improvements 

 upon his electrometers and their application, he would be much pleased. 



+ Vide Opere del Volta, torn i. parte 2. p. 33 et seq. 



X The oscillations of the index between the 30th and 35th degi-ees, sometimes during a 

 heavy shower, plainly show that the electricity of the conductor is washed off, as it were, as 

 fast as brought. 



§ I have strong hopes that our principal use of all these electrometers will i)e that of com- 

 paring them with one torsion electrometer, alluded to in my former communication. 



J 



