48 Account of an electrical Increaser for the unerring 
properties to the late Earl Stanhope, in the course of a correspon- 
dence with which for many years he had honoured me. 
I am very much obliged by your polite offer of presenting Mr. 
Tilloch with certain explanatory extracts from my letters to his 
Lordship upon this subject ; which extracts I now inclose you, to- 
gether with a drawing of the increaser. 
Earl Stanhope, after reading my letters *¢ with attention,’ was 
pleased to consider the instrument of ‘ great utility ;”’ and I shall 
feel much gratification should it be so esteemed by you, sir, as 
well as by every other scientific person for whose perusal this 
paper is intended. ; 
I have the honour to be, sir, 
Your most obedient servant, 
George Pearson, Esq. Hewry UPINGTON, 
M.D. F.R.S., London. 
Extracts from Mr. U.’s Letters to Eari Stanhope. 
«Blair's Hill, Cork, Oct. 12, 18T0. 
“ Your Lordship must no doubt be aware, that although our 
most improved condensers [composed of two parallel perpendi- 
cular metallic plates of six inches diameter each, one insulated, 
the other not ; connected at’ pleasure with two similar plates of 
one inch and a half diameter each, attached to a gold-leaf elec- 
trometer] will discover the existence of exceedingly weak and 
diffused electricity (atmospheric for instance), yet a minute por- 
tion of excited fluid, such as that produced by the contact of 
two small pieces of metal, too weak to affect an electrometer, 
must require the assistance of an increaser to manifest its pre- 
sence. 
“* Your Lordship must also be aware, that every instrument 
of this kind hitherto invented, including even Cavallo’s among 
the number, is so very defective as scarcely to merit our con- 
sideration ; while that species of multiplier called a doubler is 
totally useless, affording, as it does, the most equivocal results. 
The ingenious philosophical instrument-maker Mr. Cuthbertson 
was indeed so sensible of the inefficacy of every known doubler 
and multiplier, that he has not even hinted at either ¢erm in his 
recent publication called “* Practical Electricity.” An instru- 
tent, therefore, to answer this desirable end has much engaged 
my attention; and I have the pleasure to. say that [ have suc- 
eceded to my wish. 
“ To give your Lordship a comprehensive idea of its pro- 
perties, I shall view it in a three-fold capacity, viz. as a source, 
a carrier, and a reservoir; the stationary brass plate A of one 
inch and three quarters diameter, vertically erected on a varnished 
glass pedestal, serving as the source ; a revolving insulated brass 
’ plate 
