414 M. R. Kohlrausch's Theory of the 



might be completely moistened. If analogous to the influence 

 of cements, one would expect that in this case the proportions of 

 the residues would be different from those when, between the 

 surfaces of the mercury and the glass, a thin and dry stratum of 

 air must have been interposed; for it may be here remarked, 

 that before pouring in the well- dried mercury, the glass had 

 been washed with distilled water, heated, and sucked dry by 

 means of a glass tube. No diflfereucc however was observable in 

 these two cases ; the residues formed in the same time had just 

 the same magnitude, as may be seen from the following num- 

 bers, which refer to a case where, at both times, the charge at 

 first imparted had been allowed to stand for 606 seconds : — 



Water . 

 Mercury . 



Here, indeed, the mercury appears to have the advantage, 

 though the circumstance may probably be attributed to the 

 areat difficulty of constructing two Leyden jars with exactly 

 equal magnitudes of coating, the one with an adhering, and the 

 other with a non-adhering liquid. 



The question as to the influence of the cement would be 

 answered most decidedly by coating a glass plate on both sides 

 with amalgam, and after examination replacing it by tinfoil. It 

 will, we think, be difficult to find any measurable difference. 



§8. 



The magnitude of the residue appears to depend most essen- 

 tially upon the thickness of the glass, the flicker glass pro- 

 ducing the greater residue. The experiment about to be cited 

 on this point is not quite decisive, for the amount of I'csidue, of 

 course, depends very much upon the kind of glass ; and the two 

 bottles which were compared should, on this account, have been 

 blown from the same mass of glass, and cooled in exactly the 

 same manner. Although this was not the case, yet the interesting 

 result which was obtained may here be mentioned. 



The mean thickness of glass of the bottle b, so often referred 

 to, was 2" 7 millims. This was found from the absolute and spe- 

 cific gravities, as well as from direct measurements. The interior 

 surface, so far as it can be considered as coating, has been 

 already stated to contain 230 square centims. 



Another bottle, <?, of thin glass had a mean thickness of 0*82 

 millims., and an interior surface of 230 square centims. 



Both bottles were converted into Leyden jars by filling, and 

 suiToundiug them with acidulated water ; and by the methods 

 described in Appendix I. and II., it was found that the quan- 



