104 Experiments on the Relation between 
copper, and turnings of iron made with a dry tool, were em- 
ployed in successive experiments. The open extremity of the 
tube was drawn out to a point, and recurved, so as to pass un- 
der a vessel inverted on the mercurial pneumatic trough. Be-. 
tween this and the portion containing the metal, there was a 
length of six or more inches of tube, which was kept cool. In 
one variation of the experiment, a tube of Reaumur’s porcelain 
was used for containing the materials, to which was firmly luted, 
by a collar of caoutchouc, a glass raion with a little globe bike 
in its middle, and its loose end plunged, as usual, into the mer- 
curial trough. 
When tubes of crystal glass were employed, the part contain- 
ing the materials. was lodged in a semicyliudrical case of iron, 
which traversed a small charcoal furnace five or six inches in 
diameter. The metallic laminz being raised to full ignition in 
day-light, the case and tube were slightly moved forward, in 
order to bring a little of the salt within the sphere of the heat. 
Great nicety was required in the advancement of the sealed ex- 
tremity; for the glass tube being perfectly softened in its middle, 
too sudden volatilization of the salt never failed, by inflating and 
bursting it, to spoil the experiment. This necident frequently 
happened. On the other hand, if the central part of the tnbe 
was exposed to merely a dull red, the experiment would not sne= 
ceed with silyer and copper. At this temperature they did not 
decompose the sal ammoniac. When, however, the above-men- 
tioned precautions were observed, dew could be perceived to 
settle speedily on the cool portion of the tube. This dew be- 
came more and more visible as the sublimation advanced, till, 
finally collecting into distinet drops, it trickled down the aides 
in strie, and formed a filament along the bottom. To obtain 
good results of this kind, four or five hours must be devoted to 
one experiment, in which 20 grains of salt, and from 60 to 100 
of metal, are employed. More rapid transmission of the salts 
effects mere sublimation. Bubbles of gas come over, which, with 
silver and copper lamina, are found to be a mixture of ammonia 
and hydrogen. In this case, the liquid condensed is water of 
ammouia. 
The metallic lamine are evidently heavier than before their 
introduction ; but the increase of their weight could not be ex- 
actly ascertained, because a portion of the silver or copper is 
impressed on the i inner surface of the tube, giving it a very beau- 
tifal iridescent and metallic lustre, similar to the colours of the 
diamond beetle viewed in a microscope. The silver lamin 
-have for the most part exchanged their native brilliantwhite, for 
a dull brown or grayish hue; and, instead of being eminently 
tough and ductile, have become more brittle than any substance 
with 
