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quence of the mechanic treatment to which the material has been 
submitted. This slide was the first which was no longer ground 
with carborundum-powder, but only filed. 
The ordinary bronze for coining (see fig. 3) equally shows a struc- 
ture in which the mechanic operation is visible, both in its crystal- 
formation and in the position and direction of the crystals, where 
the more or less flattened parts meet. 
From a piece of cast-bronze of a connecting rod a thinnest possible 
sheet was filed and polished; after heating, stuck on a slide-glass 
and submitted to etching by electrolysis. A beautifully executed, 
right-angled lace-work remained, very typical for bronze structures. 
The encompassing matter of high tin-percentage had been etched 
away; the crystals, rich in copper, had remained. From a piece of 
heavily wrought phosphor-bronze, which had remained unaffected by 
colouring, I have obtained a slide with such a strong relief, that 
I have not succeeded in taking a photography of it. Also here even 
the bare eye could see the right-angled structure. The arrangement 
of the erystals was like that of tiles on a roof. 
On account of the great practical use made of white-metal in the tech- 
nical branches, I have experimented also with that. After half an hour 
also here, intact cubes of alloy of tin and antimony outlined themselves; 
also. here it was possible to go on etching very deep and without 
much difficulty to detach the cubes, entirely intact from the alloy. 
The little time left to me for the moment, necessitates my putting 
off the analysis of those cubes till later. 
Whereas at the beginning only copper-tin and copper-zine alloys 
were etched, now also iron has been experimented with. The fact, 
that it is fine-grained, that the etched facets easily oxidize, that base- 
metal-deposits *) are apt to be formed, all that naturally causes 
difficulties. The use made of salt-solutions, as electrolyte, to diminish 
the internal resistance, has yielded no result worth mentioning 
I have submitted to etching a piece of an iron-bar rolled square. 
After a few hours the fibrous structure was distinctly visible 
with the bare eye, both lengthways along the fibres and crosswise, 
vertically on them. With some difficulty I succeeded in isolating 
iron-slivers, which, if only collected in sufficient quantity, might be 
analysed quantitatively. A socle of a gaspipe sawed through, showed 
cubes in the profile: all the crystals having grouped themselves 
in the rolling-direction. A piece of a steel angle-iron having 
been submitted to the bending-test, yielded no other result as 
1) For on account of the corroding influence of acids on iron and steel a very 
small quantily of sulphuric-acid can be experimented with. 
