C 451 ] 
experiments, is fufficient to caufe an unfavourable 
alteration j by the moifture condenfing upon it. 
We are not told of what materials your pincers * 
were made, but I fuppofeof fomeeledric fubftance; 
otherwifein removing the Tourmalin from time to 
time, they may interrupt the experiment, by conduc- 
ing away the fluid. And even fuppofing them made 
of an eledtric fubftance, the unavoidable fridion may 
poflibly difturb the experiment. I have therefore 
always preferred a different method, which will ap- 
pear prefently. 
I fhall now comply with the promife I made in 
the beginning of this letter, to acquaint you with 
fome Ample and interefting experiments upon the 
Tourmalin: moft of them were made during the 
froA in Nov. laft, in confequence of an appearance 
which I then obferved accidentally. 
With me it has been always found moft conveni- 
ent to flx the Tourmalin at the end oj a long flick ofl 
the hardefl kind of Sealing-Wax , and when I am not 
ufing it, to put the other end into the top of a can- 
dleftick, or other fuitable ft and ; that the [tone may 
be the lefs expofed to any kind of fridion (See fig I.) 
And it is a rule with me never to take hold of the 
Sealing-wax, or even to touch it, but by ihat end 
(d ) the fartheft from the Tourmalin. One day on 
* J’emploie encore de petites pincettes ABC, pour ne pas 
toucher la Tourmaline avec les doigts, er je la prens toujours par 
les cotes, comme il eft indique dans la Fig. III. afinque la pierre 
foit touchee le moins qu’il eft poffible par des corps non eledri- 
ques. II faut encore avoir un Tube de verre et un baton de cire 
d’Efpagne tout prets, pour qu’on puifle examiner de la maniere 
que nous decrivons plus bas l’elpece d’Eledtricite produite par la 
Tourmaline , 
removing 
