122 REPORT — 1844. 



The Principal Conductor, &c. 



The principal conductor, DD (fig. 2), and H (fig.]), is a conical tube of 

 thin copper 16 feet high. E E (fig. 2) is a strong brass tube into which D D 

 is firmly secured, and enters about 3^ inches, but is removeable at pleasure. 

 F F is a well-annealed hollow glass pillar, whose lower end is trumpet-shaped 

 and ground flat; it rests upon the centre of the pedestal G G G, where it is 

 firmly secured by eight bolts,y',y, &-c., passing through a strong wooden 

 collar, y^, and the table of G. This pillar, with its high conductor, has re- 

 sisted gales which were strong enough to blow down large trees in the neigh- 

 bourhood ; a certain degree of flexibility in the conductor diminishes the 

 danger of the glass breaking considerably- A collar of thick leather is 

 planted between F and the table, and some strips of leather are interposed 

 between the excavated interior of the collar and the trumpet-shaped part of 

 F (as seen in the plan annexed). 



H (fig. 2) is a spherical ring fitted on the brass cap of F, and carrying 

 III, which are three of four arms at right angles with each other. I (Plate 

 XXXII. fig. 3) is a section of one of them, and of the ring H, to which it is 

 firmly attached by means of a strong iron screw R, and the plug S. K is a 

 ball fixed on the other end by means of a screw, L passing through its neck 

 and a plug M. N is a cylindrical plug sliding accurately into K, and furnish- 

 ed with a screw w\ which passes through a stopper O into a clamping-ball P. 

 K and N are perforated to fit the sliding arm Q. 



It is evident that by these means Q can be adjusted to any angle, with, and 

 its ends to any required height, from the table of G G G ; also that it can be 

 very firmly secured without being galled. 



K (fig. 2) is a little lamp for warming F F appropriately, /i' its chimney of 

 copper, closed above, passing through the table of G and entering, but not 

 touching, F. 



By this arrangement the lower part of F is generally warmed too much 

 and the upper too little ; but the pillar F being conical, <S:c., some zone always 

 exists between the two ends, which is in the best state of temperature for 

 electrical insulation*. 



L is a pair of finely pointed platinum wires soldered to D. 



M is Volta's small lantern, fitted to a ring m^, from which it can easily be 

 withdrawn when lowered by a person mounting the steps on the dome, »r its 

 lamp ; w^ is a ring or tube sliding freely on D, and attached to M, &c. ; 

 m^ is a silken line fastened to m^, passing over a pulley (from which it cannot 

 escape) at wi', descending the interior of D and E, and winding upon a reel 

 contained in the ball m®, worked by a winch a.tm?, for the purpose of raising 

 and lowering M. 



N is an inverted copper dish or parapluie, with a smooth ring on its edge, 

 fitted by a collar and stays on E, and (of course) insulated by F : its least 

 distance from a} is 3 inches. 



One of the chief objects of this arrangement is to insulate the active parts 

 of all the electrometers and the conductor itself by a common insulator, viz. 

 the glass pillar F. The cord being contained in the tubular rod, cannot dis- 

 sipate electricity from its fibres, and everything is well-rounded. 



* Mr. Read imagined (vide his ' Summary View,' &c. p. 105) "that if the insulation of 

 his rod could be constantly kept in due temperature, it would always be electrified; but that 

 that could not be done without the aid of common fire, which in so large an apparatus would 

 be very difficult." 



I believe we may safely affirm, that with the exception of a few hours of drizzling weather 

 sometimes, and on occasions when our conductor has been touched, our rod has been every 

 day, and all day, sensibly electrified since the moment of its erection (in June 1813). 



