[ 443 ] 
the exigence of this impermeability, though you 
differ from him in many other points : and refer to 
your Eflay upon the Theory of magnetifm and electri- 
city. ^ ou then relate two experiments, one with a 
wire, and the other with a glafs tube, or cylinder of 
wax: and obferve that the firfl may be eafily elect- 
rified, and the latter alfo, though with great diffi- 
culty, to any confiderable length. You then draw 
this conclulion from the two experiments, that the 
eleCtric matter pervades metals and other non-eleCt- 
ric bodies, and expands itfelf in them with the great- 
eft eafe and rapidity. But that on the contrary it 
pafes through glafs, wax, and other eleCtric bodies, 
more fowly and with much greater difficulty. 
This conclufion, inftead of eflablifhing the im- 
permeability of glafs, moft evidently affirms the con- 
trary : for though, according to your obfervation, 
the fluid pafles more fowly and with much greater 
difficulty through glafs than iron ; your admitting 
that it does pafs at all through the glafs , ends the 
difpute, as to the point of permeability : and at the 
fame time efablijhes my doCtrine of reffance ; at lead 
in glafs, and reflnous fubflances. 
In regard to my experiments upon the Tourmalin, 
you fay * that the firfl; and fecond correfpond with your 
difccverics. 
pas etre prife pour une hypothefe. C’eft une loi, prife immediate- 
ment et d une maniere inconteftable, de l’expericnce. 
Cette propriete des corps eledtriques par eux memes, eft felon 
yroi lameme que celle, queFrancklin a appellee d’un autre nom, 
impermeability. Au rnoins, je ne fais confifter Fimpermeabiliie 
en rien autre chofe, qu’en cela. 
* Je viens aux experiences de Mr. Wilfon. La premiere et 
la feconde s’accordent tout a fait avec mes decouvertes. 11 n’en 
L 1 1 4 cii 
