126 REPORT — 1844. 



fitted to a bottle D with metallic base, and is provided with a pair of gold 

 leaves rather too short to reach the sides of the bottle, the neck of which, 

 both inside and out, is also coated with sealing-wax as usual. 



This distinguisher is charged every morning negativelj', and never fails to 

 retain a good charge for the twenty-four hours. It is conveniently placed 

 upon a bracket, a few feet distant from the conductor, &c., to which when 

 used it is approached by hand, to some distance proportionate to the height 

 of the charge. If the charge is positive, the leaves of course collapse more 

 or less, but open again when withdrawn ; and if it be negative, the divergence 

 increases, &c. 



Perhaps this mode of distinguishing is preferable to Beccaria's method of 

 the star and brush, or even to that of the dry electric column, &c., for the 

 operation can be performed without ihe least danger of lowering the tension 

 of the conductor or injuring the gold leaves, let the height of the charge 

 be what it may *. 



Electrograph. 



Ah electrograph (fig. 12), of the kind proposed first I believe by Laii- 

 drlani and afterward by Bennet and Gersdof (but of which no particulars 

 seem to have been published before 1823 1)> has also been used, but not ex- 

 tensively, for reasons M-hich will be hereafter explained. 



A is a plate of tin coated with a thin layer of shell-lac, &c., as carefully as 

 possible deprived of air-bubbles, flaws and inequalities. B is a case con- 

 taining a time-piece moved by the weight C. D is part of a triangular little 

 frame fitted to the hour arbour of the time-piece and supporting A. E F is 

 a bent lever whose fulcrum is at e', below its centre of gravity : the part F is 

 of coated glass. G is a ball through a groove of which E F passes, and G 

 is supported by a cross arm of the conductor. 



When this instrument was used, the end E was allowed to rest with very 

 little pressure upon A, which being carried round by the clock became elec- 

 trified in the line and neighbourhood of its contact with E to an intensity 

 proportional to the charge of the conductor. After having been allowed to 

 perform a full revolution, or any given part of one, under these circum- 

 stances, A was removed from D and well-powdered with chalk, projected 

 upon it from a lump rubbed upon a hard brush. The powder, of course, as in 

 Lichtenbourg's figures, adhered almost exclusively to the parts which had been 

 more or less electrified by and in the neighbourhood of E ; and a figure was 

 produced, of which a calotypic image, kindly executed for me by Mr. Collen, 

 by means of his camera obscura, Sec, is preserved as a specimen. Many such 

 images could be produced in a few fine hours from A, and thus a sort of 

 pictorial register of atmospheric electricity (of serene weather at least) be 

 circulated amongst meteorologists, care being taken of course to note the 

 time of putting on and taking off the resinous plate. 



That figure was made contemporaneously with hourly observations of the 

 voltaic electrometers. The plate, after the powdering, was placed upon a 

 circular paper, divided as the hours of a dial, and the intensities (as 35°, 25'^ 

 16", <S:c.) were marked against the appropriate hour, by which it may be 

 seen that, excepting at the hour of six, the breadth of the line or figure cor- 

 responds pretty nearly with those intensities. 



* Indeed I do not know whether some some such contrivance might not he applied to 

 measure as well as distinguish the charge of the rod ; particulariy if the insulation of the 

 gold leaves were preserved hy means of chloride of calcium in a manner hereafter to he 

 spolicn of, the distance from the rod heing made the measure of tension. 



t Vide Descriptions of an Electric Telegraph, &c., p. 47. 



