410 Prof. Faraday on the Experimental Relations 
Deflagrations of Gold (and other metals)—heat—pressure, &c. 
Gold wire deflagrated by explosions of a Leyden battery pro- 
duces a divided condition, very different to that presented by 
gold leaves. Here the metal is separated into particles, and no 
pressure in any direction, either regular or irregular, has been 
exerted upon them in the act of division. When the deflagra- 
tions have been made near surfaces of glass, rock-crystal, topaz, 
fluor-spar, card-board, &c., the particles as they are caught are 
kept separate from each other and in place, and generally those 
which remain in the line of the discharge have been heated by 
the passage of the electricity. The deposits consist of particles 
- of various sizes, those at the outer parts of the result bemg too 
small to be recognized by the highest powers of the microscope. 
Beside making these deflagrations over different substances, as 
described above, I made them in different atmospheres, namely, 
in oxygen and hydrogen, to compare with air; but the general 
effects, the colours produced, and the order of the colours, were 
precisely the same in all the cases. These deposits were in- 
soluble in nitric acid and in hydrochloric acid, but in the mixed 
acids or in chlorine solution were soluble, exactly in the manner 
of gold. There is no reason to doubt that they consisted of me- 
tallic gold in a state of extreme division. 
Now as to the effects on light, 7. e. as to the coloured rays 
reflected or transmitted by these deposited particles, and first, of 
those in the line of the discharge where the wire had been. Here 
the mica was found abraded much, the glass less, and the rock- 
erystal and topaz least. Where abraded, the gold adhered; in 
all the other parts it could be removed with the slightest touch. 
The gold deposited in this central place was metallic and golden 
by reflected light, and of a fine ruby colour by transmitted light. 
On each side of this line the deposit had a dark colour, but when 
particularly examined gave a strong golden metallic reflexion, 
and by transmission a fine violet colour, partaking of green and 
ruby in different parts, and sometimes passing altogether into 
green. Beyond this, on each side, where the tints became paler 
and where the particles appeared to be finer, the transmitted 
tint became ruby or violet-ruby, and this tint was especially seen 
when the deposit was caught on a card. As to the reflected 
light, even at these faintest parts it is golden and metallic. 
This is easily observed by wiping off a sharp line across the 
deposit on glass in the very faintest part, and then causing the 
sun’s rays collected in the focus of a small lens to travel to and 
fro across that edge; the presence of the metallic gold on the 
unwiped part is at once evident by the high illumination pro- 
duced there. It is evident that all the colours described are 
