(6q6) 
And now , Sir] feeing the want of Shining Wood hath kept 
me ever fince I Cent you the former Experiments from making 
any New ones on that fubje& , I (hall 5 by way of amends , fub« 
joyn fome of the Obfervations , that I heretofore intimated to 
you, I had made of the Refemblances and Differences between a 
Live Coal and a Piece of Shining Wood $ in perufing of which yon 
v ill eafily difcern , that to thofe Particulars > which my Memo- 
ry and the former Obfervations , I had noted down abdat Light 
and Luminous Bodies^ had fuggefted to me , I have added fome, 
that have been afforded me by thofe lateTryals, made in my 
Engine , whereof I feat you an account* - 
Refemblances . 
The things , wherein I obferved a piece of Wood and a Burn- 
ing Coal to agree orrefemble each other, are principally thefe 
Five. 
1 . Both of them are Luminaries, that is, give lights as having it 
(if I may (0 [peak ) reading in them, and not like Looking- Glaffes or 
White Bodies , which are confpicmus onely by the incident beams of 
the Sun , or fome other Luminous Body , which they reflect. 
This is evident , becaufe both Shining Wood and & Burning 
Coal , fhrne the more vividly , by how much the place , wherein 
thiy are put , is made the darker by the careful exclufion of the 
adventitious light* 0 Tis true , that the Moon and Fensts appear 
brighteft at or about Midnight , and yet have but a borrowed 
light 5 but the difference between thofe Planets and fhe Bodies we 
treat off, in reference to the difficulty we areconfideringjs obvi- 
ous enough. For , though the Beholders eye that looks upon 
thofe Stars, be advantag’d by being in the dark , which enlarges 
the Pupil of the Eye , yet the Ob je< 5 t it felf is freely expofed to 
the beams of the Sun , which if they were intercepted , thofe 
Manets would Quickly be darkned 3 as experience manifefls in 
BcUpfes, 
2:. Shining Wood and a Burning Coal , need the pre fence 
of the Air , and ifre too of fuoh a denfity , to make them continue 
jhming o 
This has been proved as to a Coaly by what I longfince pub- 
Hilui in my Phyftco Mechanical Experiments^ where I relate. How 
quickly 
