[ 3 ° ] 
When I made ufe of the glafs Tube, as the Quantity 
was lefs, fo the Sparks were finer, lefs in Thieknefs and 
in Length, but much more adive ; nor did they pro- 
ceed fo regularly towards the Tube, nor make fo 
regular an Appearance (being feldom, if ever, alto- 
gether regular, as the others) ; frequently breaking in 
Pieces, as if by Collifion, or not altogether unlike 
the Sparks from a Brand in a Wood Fire, which has 
lain long without being ftirred. Another Difference 
I remarked was, that the relinous Effluvia were more 
deeply coloured than the vitreous. 
Whether it be not probable, that the refinous 
Effluvia are more unduous or fulphureous than the 
vitreous ; and becaufe not fo adive and nitrous, lefs 
apt to kindle inflammable Spirits, as I think I found 
them to be ? 
I intreat I may not be confidered as pretending, 
in the above Trials, to eftablifh Laws, but, as plainly 
relating Matters of Fad. Perhaps future Trials may 
not confirm thefe. 
I think it not a Circumftance too impertinent to 
be mention’d, that the Trials relating to Repulfion 
were made in a fmall Room, and near a Fire 5 the 
Air pretty moift. 
Dear Sir, 
fooling, Jan. 1 5 , 
1745-6. Tour moji affectionate Friend, 
and obliged Servant, 
H. Miles. 
II. 
