472 REPORT—1883. 
which has been usually regarded as amorphous, is either built up of crystalline forms, 
or, as has been suggested to him by Professor T, G. Bonney, the amorphous silica 
in the glass rearranges its molecules and becomes crystalline. 
10. On certain Molecular Movements in the vicinity of thin Iron Plates. 
By Witt1am THomson, F.R.S.E. 
The experiments described in this paper were a continuation of those made by 
the author some time ago, the results of a number of which were brought by him 
before this section two years ago. At that time he was under the impression 
that certain phenomena which were produced by leaving iron in contact with 
wet prussian-blue dyed cloth resting on wet blotting-paper, appeared to be 
due in some way or other to magnetic action, which had directly or indirectly 
caused the well-defined lines of insoluble prussian-blue which appeared to have 
flowed from the iron into the blotting-paper underneath the cloth. Since then 
he has made experiments with iron strongly magnetic, and simultaneously with 
similar pieces of iron which were only magnetic from the action of the earth’s 
magnetism, In each case the lines of colour were produced, but they developed 
to a greater distance, and much more regularly, from the piece of iron which was 
very slightly magnetic, than from the one which was strongly magnetised. 
In one series of experiments slips of thin iron, 32x 3x °0075 inch, cut from 
ferro-type photograph plate cleaned and polished, were placed on slips of 
glass and covered by thin layers of glycerine jelly, coloured by prussian-blue 
(which was developed by the action of potassium ferricyanide on ferrous sul- 
phate), containing also a slight excess of ferricyanide, and made faintly acid 
with hydrochloric acid. One of these was laid aside, and the other supported 
on the poles of a horse-shoe magnet placed with its poles upright, the glass 
being kept in position by the action of the magnet on the slip of soft iron on 
the other side of the glass: the slip of soft iron was thus rendered magnetic. In 
each case a deep-blue colour extended out from the iron all around, forming an 
oval, but the colour extended more rapidly from the iron which was not rendered 
magnetic, than from the other which was magnetised. The colour then collected 
round the margin of the oval from the former, and became most intense at the two 
ends. Four well-defined thin straight lines of the prussian-blue colour then developed 
from the ends of the oval, going towards each other at an angle of about 45° from 
the line of the metallic slip till they came to the margin of the jelly on the glass ; 
and some weeks later other well-defined but curved lines developed from the ends 
of the oval, which gradually exfoliated until five had formed at each end of the 
oval going in beautifully formed curves to the edge of the glycerine jelly. The 
slip placed over the magnet formed a deep-blue oval round the iron slip ; about one- 
half the area of the oval ultimately formed round the non-magnetised slip, and no 
lines of colour developed from it. 
Presumably the deeper blue developed around the iron in these two experiments 
was due to the action of the acid upon it, and the combination of the ferricyanide 
with the iron thus brought into solution. Another similar experiment was made 
by using the same proportion of ferricyanide and acid, but without the addition 
of ferrous sulphate to colour the jelly blue. In this case prussian blue formed a 
thick coating on the top of the iron slip, but it did not extend outwards from the 
margin of the slip. In a third experiment a drop of jelly, deeply coloured with 
prussian blue, was placed on the surface of transparent glycerine jelly, but 
after nearly two years the colour had not extended in the faintest degree into 
the colourless medium. In a fourth experiment a slip of blotting-paper, the size of 
the iron slips used in the first-mentioned experiment, saturated with a solution of 
ferrous sulphate and dried, was placed in part of the coloured jelly mixture 
first mentioned. A blue colour, deeper than that of the surrounding jelly, 
gradually extended outwards, forming after a few weeks a small oval round the 
paper, which did not increase in size or undergo any further alteration after two 
years. 
