i oja J Mr. henly’s OBfervations 
affected by a fluid acting immediately upon them 
through giafs \ or by acting upon them immediately by 
the giafs, as above mentioned. 
E X P E E I MEN T. 
A circular box, three or four inches in diameter, 
and a quarter of an inch deep, is fur nidi ed with a 
thin giafs for a top. In this box flatter fome very 
final! fteel filings, or lift them into it through a piece of 
Writing paper, which has a number of holes pricked 
through it with a pin. Then apply one of the ends of a 
magnetic bar to the upper furface of the giafs ; the filings 
will be inftantly attracted to the giafs, and remain there 
as long as the magnet is thus fufpended over them ; but 
the moment it is removed, the filings fall to the bottom 
of the box, and there Eemain at reft. The giafs then being 
made perfectly clean and warm, let a fine piece of am- 
ber, fealing wax, &c. be ftrongly excited and applie d to* 
it as the magnet was in the former experiment; the 
filings will be inftantly in motion, and will continue fo 
for fome fleonds. When their motion ceafes, withdraw 
the amber, 8cc. and the motion of the filings will be re- 
newed, and continue as at firft; this lhews,l think, that in 
3 hoth 
