( ) 
Glafs : Bat now a Circle of Light would difcover it 
^eU juO: on the edge of the Pitch which feperated it from 
the tranfparent Part, as likewife another ring of Light 
fomewhat nearer to the Axis of the Glafs, but both thefe 
when the Hand was apply’d to the under part 5 for when 
it was remov’d to the contrary, no fuch appearance enfu’d. 
The tranfparent half of the Glafs was in allCircumftances 
as in former Experiments. When all the Air was let in, 
the Elcdtricity of the Glafs in all its parts, the Lin’d as 
well as the Tranfparent, performed much alike. The 
Threads feem’dto be attracted every where with equal 
Vigour. To conclude^ this, and the foremention’d Ex- 
periment of the Sealing-wax, plainly difcover, a tranfpa- 
rent Quality in foine Bodies fwe call Opake) under fuch 
and fuch Circumftances : Bodies which arc really Opake, 
have hitherto been thought to continue always fo. It was 
never fo much as fufpefled, that they could exchange 
that Quality for the contrary one, and then come back 
from that .contrary one to their old State again e* That 
theyfhould pafs from Opake to Pellucid, and from Pellu- 
cid to Opake ^ atone time admit, and at another time op- 
pofe the paflage of Light : And all this by a meet change 
of external Circumftances. This Property I fay is as new 
as ’tis real and furprizing ; and the bare confideration of 
fo very unlikely and unexpected a thing, may be a ground 
of encouragement to hope, that fome other odd Proper- 
ties of Bodies, by fome lucky Trials, may hereafter fas 
this has donej furprize us with a difeovery of them- 
fdves. I fhall only add, that what is faid towards a 
Ileafon of fuch an Appearance in the Experiment of the 
Sealing-wax, 1 think is very applicable to this^ to which 
1 refer. See Phyf co-mechanical Experiments on various 
Suhje^s, ?2ig, 1^1^ 
IV. A 
