Defcription of a newly invented Galvanometer. 39 



had frequently occafion to make ufe of the gold-leaf electro- 

 meter invented by Mr. Bennet. 



f had often been wifhing that fome inftrument could be 

 devifed to meafure the galvanic action of a plate of filver and 

 one of zinc, when connected with the tongue and upper lip; 

 and as fome philofophers had all along maintained that the gal- 

 vanic and electric fluid were the fame, the delicate fenfibility 

 of the gold-leaf electrometer fuggefted the idea of accommo- 

 dating it to the object I had in view, for which purpofe I 

 adopted the following conftruction : 



Fig. 1. (Plate I.) reprefents the galvanometer complete, 

 the top or lid, to facilitate the defcription, being mown above 

 the glafs cylinder inftead of being infertcd in its mouth, as it 

 is when the inftrument is in ufe. The top confilts of two 

 circular plates of brafs fattened to each o>her, and attached 

 to a cork which fits into the cylinder. The undermoft plate 

 has an oblong hole cut though it (as has alfo the cork), and 

 from this hole a groove pafies to the outer edge of the plate 

 to admit a thin flip of filver A A, and allow it to Hide back- 

 wards or forwards between the plates, for the purpofe of 

 moving the gold leaves a, attached to the iilver, nearer to or 

 further from the upright pieces B and C. This part of the 

 conitruction is alfo fhown in fig. 2. which reprefents the me- 

 tallic part of the cover inverted, AA being the flip of filver. 

 One end of the filver, viz. that which defcends into the cylin- 

 der (fig. 1 .), is flit, for the purpofe of receiving the gold leaves. 



BB, CC, are two pieces of zinc, the uprights of which can 

 be made to approach to or recede from each other by means 

 of a Hide in the tranfvp.rfe pieces at the bottom of the jar, and 

 which is rcprefented in fig. 3. The two pieces of zinc are 

 kept at the diftance defired by means of the fcrew D, fig. 1 

 and 3. 



The zinc BB, properly fpeak.ing, is of two pieces, attached 

 by a joint at E to facilitate the arrangement when the intiru- 

 ment is intended to be put in action. 



The bottom- part ?;*, which receives the glafs cylinder, is 

 of box-wood, and is furnifiied with glafs feet, FFF, for the 

 purpofe of occasional inhalation. 



The inftrument being fitted up to my liking, I tried its 

 effect by introducing the exterior end of the flip of filver be- 

 tween my upper lip and gum, and laying the moveable piece 

 of zinc upon my tongue. The diftance of the two pieces of 

 zinc was i-4th of an inch. I could not perceive the fmalleft 

 effect to take place. I tried it with the zinc pieces 1 -8th of 

 an inch afunder, and alio at the diftance of i-i6th, but ftill 



C 4 without 



