252 Proceedings of Boy al Society of Edinlurgh, [march 19 , 
thirty or forty days], demonstrate (1) the retardation which takes 
place in the ascent of HCl into jelly coloured yellow with methyl 
orange; (2) which demonstrate that the results by the silver nitrate 
methods corresponds closely with those obtained by the diffusion 
of same acid into jelly coloured with methyl orange. The same 
table also contains results of diffusing HgSO^ into jelly impregnated 
with barium nitrate, and of diffusing KCl, NaCl, SiCl and MgCl 2 
into jelly impregnated with silver nitrate. 
In point of fact, when jelly is used the methyl orange method 
and the silver nitrate and barium nitrate methods are about on a par, 
so that the two latter become very useful in making experiments of 
a comparative nature with neutral salts, either for investigation or 
lecture illustration. 
The principal results I have obtained, together with some of 
those obtained in the paper read July 15, 1887, are given in the 
diagram of curves herewith, in w^hich the vertical lines represent 
time, and the horizontal lines height of diffused columns in milli- 
metres. The observations were taken daily, and the regularity of 
the curves came out wonderfully in accordance with theory. 
[Diagrams 
