On De Lue’s Electric Column. 197 
Tang B = tang A cot 34. Tang B’ = tang A’ cot $8. 
_C = (B’+ B + $) and D = (B’ — B). 
4 _ — sin(d+9)sin(A—@)sinD 
Tang E = yeast 5 cos § (C+ D) cos $ (CD) 
Cos (2A—C) = oT es = cos (C — 2A). 
Tang (A—iIC)= + y (tang}Dtangi (D—E). 
cos $ (h + 6) sind (h—39) sin D 
c—D 
cos ¢sin (A - > ) cos £ (C+D) 
Of the two values of a, the one is chosen which makes (45° 
— 19) 4 45°; that is to say, 9 positive. Those formulzare 
purely analytical, at least it is difficult to perceive in what 
they could assimilate to the ordinary solution. They are 
elegant; they indicate, in a more direct manner than any 
of the preceding methods, the choice to be made between 
the two roots of the equation, but at the same time re- 
quire too long a preparation, more logarithms, and have 
besides that great inconveniency, in a method of common 
use, that it cannot be retained by the best memory. This 
solution requires 29 Jogarithms absolutely different ; besides 
‘ that ten of these logarithms are to be used twice; so that, 
with all the compositions of half sams and half differences, 
the operation is longer by half than that of our formule : 
thus, notwithstanding its elegance and general application, 
I do not expect it will be preferred in practice. 
Tang (45° —1¢) = 
a 
XXXIV. On De Luc’s Electric Column. By Mr.B. M. 
FORSTER. 
To Mr. Tilloch. 
‘ 
+ Walthamstow, 16th March 1811. 
Sir, Sivce my Letter, on 4 Method of fitting up, Gc. 
the Electric Column, invented by Mr. De Luc, was pub- 
lished in your Magazine for March 1810, Mr. De Luc 
has sent a series of letters to Nicholson’s Philosophical 
Journal, on the Galvanic Pile and on his Electric Column, 
in which are several very interesting and curious particulars; © 
a few of which I shall here relate. 
He made what he calls dissections of the pile, bv means 
of tripods of brass wire. The first dissection was by placing 
the /ripods between each plate of zine and silver, thus se- 
parating groups in which the metals had letween them wet 
cloth. With this pile, the effects appeared to be the same as 
N3 in 
