2S4 1 EXAMINATION OF VOLTA's EXPERIMENTS, &C. 



appear to me to be much inferior to one conflru&ed in the year 

 1793, by Mr. John Read, an ingenious ele&ricran at Knightf- 

 bridge ; but as he invented it near the time of his retiring from 

 bufinefs, he did not publifh it, confequently it is known but by 

 very few electricians. I have found it of great ufe not only in gal- 

 vanifm, but in ail experiments wherein fmall quantities of elec- 

 tricity are to be made evident; and I doubt not but that it will 

 be confidered as a valuable acquifition by electricians. I have 

 found it capable of rendering much fmaller quantities fenfible 

 than any other inftrument. By this inflrument we are able to 

 learn the poiitive and negative fides of only one piece of zinc, 

 copper, and wet cloth; and I have not heard that it has been 

 done by any other inflrument lefs than with a feries of twenty*. 



A Defcription and Ufe of Mr. Read's compound EleBrical 



Condenfer. 

 Fig. I. plate XVI. reprefents a vertical fe&ion of the large 

 Read's con-° condenfer: a a is a round flat plate of brafs of about eight 

 denfer. inches, (landing infulated upon a wooden foot g; g h is a hol- 



low brafs cylinder, and fh is a folid flick of glafs, with a brafs 

 mounting at/, to which the plate a a is fixed ; hb is another 

 plate of brafs fomewhat lefs in diameter, and has a round hole 

 in the middle of about two inches diameter ; c d is a hollow 

 cone fixed to b b at c c; de is a hollow brafs cylinder fixed to 

 the cone at d, and made to Aide up and down upon the cylin- 

 der gh; i is a milled head-fcrew which holds b b faft when it 

 is at its proper diflance from a a, where a flop is made for that 

 purpofe ; when i is loofe, b b falls down by its own weight, 

 and refls upon the foot g. 

 Altered by the The above is the original conflru6tion, which I found more 

 author. complex and lefs portable than I could wifh ; for which reafons 



I make them in the following manner ; and fixing the con- 

 denfing plates in a vertical pofition inflead of horizontal, it has 

 all the advantages, is more fimple, and perfectly portable, and 

 I have no doubt will meet with the approbation of Mr. Read 

 himfelf. 



Defcription of the improved Condenfer. 

 Defcriptlon of Fig. 2 reprefents a vertical feclion of the large condenfer 

 the improved ftanding edgewife to the eye: a a and b b are two flat round 



* Bennet's electrometer alone fhewed the ftate of 40 pairs. See 

 Van Marurain Philof. Journal, o&avo, I. 174.— N. 



brafs 



