[ 443 3 
In hopes the experiment here recited may be 
taken in this view, as tending, in conjunction with a 
variety of others, to illuftrate an important point, I 
beg leave to prefent it to your Lordfhipj and am, 
My Lord, 
Your Lordfhip’s 
moft obedient 
and devoted 
St. Helena, 
July 30, 1761. 
humble fervant, 
Nevil Mafkelyne. 
x 
LXVII. Observations tip on fome Gems Jimilar 
to the Tourmalin \ by Mr . Benjamin Wil- 
fon, F. R . S . 
Read Jan. 28, t" | HE honour I received from the 
I Royal Society, in confequence of 
my late papers on electricity, and which principally 
relpeCted the Tourmalin, is a plealing motive for em- 
braceing the firft opportunity to communicate farther 
enquiries, that tend to throw more light upon this 
curious fubjeCt. 
In September la ft, I met with feveral gems of dif- 
ferent fizes and colours, that refemble the Tourmalin, 
ki regard to eleCtric experiments. The moft beautiful 
of 
