124 Progress in Science. (January, 
the disk is seen. This phantom disk will appear to be motionless when the 
periods coincide; but when otherwise, it revolves in one direction or the other. 
It is obvious that the vibrations of the flame can be easily counted by this 
means. The inventor, Mr. Charles J. Watson, counted, with a sixteen-inch 
tube, 453 vibrations of the flame per second. By this instrument the undu- 
lation of the vibrations of a wire can be seen to travel up and down the wire; 
and if watched by both eyes through the slits, the spiral course of the un- 
dulations can be observed. 
F. Tommassi has described a series of experiments, illustrated by woodcuts, 
for the purpose of proving the possibility of converting into dynamical work 
the dilatation produced in liquids by heat; he proposes to utilise this motive 
force for the purpose of working hydraulic presses. 
A new application of the oxyhydrogen light to the separation of metals has 
been patented by Tessie du Motay. It is especially applied to the metallurgy 
of copper. The usual treatment of copper has had until now for its objet 
the extraction of the metal of a certain class of ores, where it is found com- 
bined with sulphur, arsenic, antimony, tin, lead, iron, &c. According to the 
new method the metal is first smelted with a flux of silicates; metallic silicates 
are formed, in which the sulphur and arsenic are eliminated and replaced by 
silicic acid. These metallic silicates are then further treated in a blast furnace, 
and submitted to the reducing property of incandescent charcoal; the metallic 
oxides are reduced in a metallic state and fused, and thus collected in ingots. 
The ingot thus obtained is composed of a variety of metals from which the 
copper has to be separated; this object is attained by smelting these ingots 
in a reverberatory furnace in the presence of atmospheric air, which oxidises all 
the metals except the copper ; it is by this process of cupellation that M. Tessie 
du Motay utilises the slowly oxidising property of the oxyhydrogen flame, in 
order to facilitate the separation of the copper; he directs the flame, obtained 
by burning a mixture of common street gas and oxygen gas, on to the fused 
mass. The combustion of this gaseous mixture furnishes a certain amount 
of carbonic acid and oxide of carbon, as well as a small proportion of water ; 
it is this water, claims the inventor, which, at the high temperature to which 
it is submitted, has the property of oxidising rapidly all the metals except the 
copper and lead. The fused metal obtained is then pure copper, if the original 
ingot contained no lead; and is composed of an alloy of copper and lead, if 
the ingot contained these two metals. 
Dr. A. Vogel records a series of experiments made to prove the well-known 
fa& that sulphuric acid is a constant product of the combustion of coal-gas, 
even when purified as perfetly as possible from sulphuretted hydrogen; the 
source whence the sulphuric acid is derived is the sulphide of carbon present 
in the gas. 
The apparent volatilisation of silicium and boron has been observed by 
L. Troost and P. Hautefeuille. They describe a series of experiments made 
with pure silicium and boron, each by itself, placed in porcelain tubes, kept at a 
very high temperature in a slow current of dry and pure hydrogen gas, and the 
reaction which ensues by the admission into the tube of fluoride of silicium, 
chloride of silicium, and fluoride of boron. Silicium is under these conditions 
apparently volatilised, forming a brown-coloured smoke, which, in a cooler 
part of the tube, is condensed sometimes as amorphous silicium, sometimes 
deposited in crystalline state. The same obtains with boron, but this apparent 
volatilisation is due to a simple mechanical effe@, conjointly withthe existence 
of compounds of silicitum with chlorine and fluorine, which are only formed at 
a very high temperature, and dissociated at red heat. 
We extraé& the following graphic description of the action of cold on vapours 
from the ‘‘ Chemical History of the Creation,” by J. Phinn, Editor of the New 
York “ Technologist.” The book is full of similar striking illustrations, and 
the subjeé is treated in a manner which makes it peculiarly interesting to 
scientific men:—‘ It is a generally received opinion that all gases are merely 
vapours of liquids that boil at a very low temperatures. Thus, while water 
boils at 212°, common ether boils at 96°, and sulphurous acid at 0°. Con- 
