causing
the new stone to become a great favorite with the fashionable. One of
Hogarth's inimitable designs depicts a spendthrift fop who has just
been arrested while his attention was riveted on the strange phenomena
shown by the tourmaline.
In
view of the important experiments made by Benjamin Franklin in the then
almost unexplored field of electricity, it is easy to understand that
the accounts of the newly-discovered electric properties of the
tourmaline should have possessed considerable interest for him. This is
testified to by a letter he addressed to Dr. William Haberden, June 7, 1759.100
Herein he expresses his thanks for two tourmalines his correspondent
had sent him, and states that he is returning the smaller one. Of the
electric phenomena he writes that he had heard some "Ingenious
gentlemen abroad" had denied the negative electricity displayed by one
side of a tourmaline, but he believes the failure to observe could be
explained by defective cutting of the specimens used, the positive and
negative planes having perhaps been obliquely placed; to obviate
this/he suggests that the positive and negative sides should be
accurately determined before the operation of cutting begins. The
larger of the specimens sent by Dr. Haberden was retained by Franklin,
who had it mounted on a pivot in a ring, so that either side could be
turned outward at will. Hè notes as a curious circumstance that when he
wore this ring, the natural heat of the finger sufficed to charge the
stone, causing it to attract light bodies. Several of his experiments
were made with a cork ball suspended by a thread, and he claims that
the attractive force, of the positive face was increased by coating it
with gold-leaf attached to the stone by white of egg. This greater effect he supposed to be occasioned by the united force of
"· The Complete Works of Benjamin Franklin, ed. by John Bigelow, New York and London, 1888, vol x, pp-282-285.
