[ H ]

'** and breadth without thickness, but when I /peak of the upper" or under surface of a piece of glass, the outer or inner surface of" the phial, I mean length, breadth, and half the thickness, and" beg the favour of being so understood.” After adding to eachsurface half the thickness of the substance of the glass, he sup-poses, that the texture of the glass in cooling, when it is firstblown, becomes closest in the middle, and forms a kind of par-tition, in which the pores are so narrow, that the particles ofthe electric stuid, which enter both surfaces at the time of thecooling of the glass, cannot go through, or pass, or repass,from one surface to the other; yet notwithstanding this, hesupposes, the particles of the electric stuid act by a repelling pro-perty on each other through the pores of the glass.

The Doctor, in 1755 9 , frankly confesses his error in the fore-going supposition, and says, he knows nothing of the nature ofthe pores of glass.

" My hypothesis,” fays he, " that the pores were smaller in** the middle of the glass, too small to admit the passage of elec-" tricity, which could pass through the surface, till it came near“ the middle, was certainly wrong —but as he could not, by anymeans he was then acquainted with, force the electric stuidthrough glass, it was concluded, that glass is impermeable tothe electric effluvia; and upon this the present Frankliniansystem rests.

As I am not attached to any man, nor any theory, any far-ther than J think it consistent with, and agreeable to the sim-ple laws of nature, I shall beg leave to with-hold my assent forthe present, and to give this hypothesis a fair and candid exami-nation, and to try if it can stand the test of a critical inquiry.

9 Franklin’s letters, p. 321.

9

CHAP-