III. An Account of an Experiment^ fhewing that 
m OhjePl may become Vifthle through fuch 
an Opake Body as ^itch hi the Darl^ while 
it is under the Ctrcumjiances of Attrition and a 
Vacuum, By Mr, Fr. Hauksbec, F. S. 
T His Experiment affords a fignal Confirmation of 
another formerly made, and differs only in the Mat- 
ter made ufe of. I before ufed Sealing-wax, but now 
made choice of Pitch, which I ferv’d as the Sealing-wax 5 
that is, I melted it in a Globe-glafs, and kept it turning 
about ’till the larger half had got a pretty thick lineing ot 
it • it was even fo thick that a Ray of Light could no 
way penetrate it. This Globe I exhaufted of its contain- 
ed Air^ then ("being Night) I put it on the Engine to 
give motion to it^ where, after it had been turn’d a little 
while, with my Hand on that half lined with the Pitch, 
I could very eafily difcover thro’ the tranfparent part, on 
the inward furface of the Pitch, the very (hape and lines 
of it, as likewifeof my Fingers^ for the moll: eminent 
Parts of the Hand and Fingers that toucht the Ghfs, ap- 
peared all luminous : The other Parts difcovered them- 
felves by the dark Intervals they made between the en- 
lighten’d Parts; And when the Fingers were fprcad or 
clos’d, ’twas very obvious to tlie Sight. Now, after a 
fmall quantity of Air was let in, the Light difappear d on 
the intide of the lined part (but not on the other,) which 
began to difcover it felf more and more on the outfide5 
tho’ even in Vacuo there was always a Light attended on 
the touch of thofe Parts that were moft contiguous ta 
