52 
POPULAE SCIENCE NEWS. 
[April, 1890. 
found seems to date from 200 B. C. Still, some of 
the establishments must have been of prior date, 
but the researches have not been complete enough 
to prove, or even approximate to correctness on this 
point. But the archieologists seem to be of the 
opinion that the T*ne was not a station such as 
those of the Stone or Bronze Ages, known as habi- 
tations where people lived in security against wild 
beasts. It is evident that they were attacked here 
and defeated by their enemies, who carried off 
everything of value in gold and silver that thej' 
could find. We read in Roman history that such 
was the custom of the conquerors ; that Marius, 
" having defeated the Cimbres, chose from the 
trophies the most beautiful arms, and burned the 
rest." The unfortunate Ilelvetes left on the marsh 
or in the river, their bodies, their treasures, — every- 
thing, in fact, that the victors did not care to carry 
with them. The waters at flood tide swept these 
bodies and objects to the bottom of the Thielle, and 
there covered them with successive layers of turf, 
sand, gravel, and mud. 
Such is the conjecture of the archaeologists, to 
whose labors we owe the fine collections in the 
museums, which give us the opportunity of judging 
for ourselves of the skill and ingenuity of this war- 
like race of the great Iron Age — the "Epoch of the 
Tene." 
SCIENTIFIC BREVITIES. 
A Dublin Trader announces on his billheads 
that, in consequence of the inaccuracy of chemical 
analysis, he has ignored such tests in favor of a 
sworn magisterial declaration regarding the quality 
of his goods. 
Another Mine of Mercury is announced as 
having been discovered in the Transvaal, at a place 
called Witkoppies, near Malmani. The yield of 
quicksilver shows that the ore is rich, though the 
mine at present is only fifty yards square. 
Electricity in the Dairy. — An interesting 
application of electricity to the dairy industry has 
been recently made in Italy. The Count of Assata, 
whose buildings are fitted up with the electric light, 
has connected his dairy plant with an electric motor 
of twelve horse-power. This machine drives a 
Danish separator and a Danish churn of the capacity 
of 400 litres of cream, churning being conducted at 
the rate ef 120 to 160 revolutions per minute, the 
butter being brought in from thirty to thirty-five 
minutes, in fine grains, which, it is now recognized, 
enables the maker to produce the finest article. A 
pump is also worked in 'the dairy. 
A New Roofing Material. — A new roofing 
material is mentioned in the German papers, in the 
shape of a sort of metallic slate, somewhat similar 
to those used among us, but enamelled so as to be 
proof against moisture or acid vapors. Metallic 
slates of tin and galvanized iron have long been used 
in Germany, and galvanizing has been pronounced 
by the highest scientific authority there, to be the 
best protection against rust that has yet been applied 
to iron, but it is acknowledged that the bending 
necessary to form the locking joints of the metallic 
tiles is apt to throw off the protecting covering, 
leaving the iron exposed to corrosion. In order to 
provide against the bad effects of this, the new- 
plates are made of sheet-iron, stamped into shape in 
the usual manner, and are then dipped into an 
enamel paint, which, when heated, forms a contin- 
uous coating, unaffected by acids or alkali»s. It is 
too soon to say how long a roof laid with such a 
material will last, but it promises to be of consider- 
able value. 
Practical Cljonjistry arid tlje Jlrts. 
AERIAL NAVIGATION. 
It may safely be said that the navigation of 
the air is a practical impossibility, and that 
no balloon, air-ship, or other means of con- 
veyance which can be propelled through the 
air in a definite direction, under the control 
of the operator, will ever be constructed. 
But, as. this method of travel is confidently 
predicted by many as a development of the 
near future, — and even now announcements 
of the discovery of a means of navigating the 
air appear more or less frequently, — a consid- 
eration of some of the theoretical principles 
involved may be of interest. 
It is evident that a practicable air-ship must 
contain within itself the power to make it rise 
in the air, as in the ca.se of a bird. No bal- 
loon could ever possibly be forced through 
the air against a wind of any velocity. The 
immense surface presented to the action of 
the wind, would require a force to overcome 
it far beyond any that we could produce ; 
and, even if it .could be accomplished, it 
wotild only result in its immediate destruc- 
tion by tearing the necessarily light and fragile 
material of the balloon into fragments. It 
would be as easy to drive a balloon at a high 
rate of speed underneath the ocean itself, as 
to make any headway against a wind of only 
moderate violence. 
It is a necessity, therefore, of a practicable 
air-ship that it must contain within itself not 
only the power to move it through the air, 
but to sustain it at the required height. A 
bird does this, it is true ; but the body of a 
bird has a very small weight in proportion to 
the force developed by its organism. It is 
like a motor which has only to move itself. 
But we have no artificial motor which can 
begin to compare in efficiency with the natu- 
ral one possessed by the bird ; and, besides, 
an air-ship must not only raise and move 
itself, — and the weight of all our artificial 
motors is very great in proportion to the 
power they exert, — but it must also carry the 
weight of passengers, baggage, supplies, and 
many other things, all of which increase the 
power necessary to raise them to an immense 
degree. Theoretically, an air-ship is possible, 
but a calculation of the force necessary to lift 
into the air even the lightest and most effi- 
cient form of steam engine known to us, will 
show that it is far beyond any power that it 
can develop, to say nothing of the addition 
of passengers or freight, and the driving of 
the whole through the air against the ever 
prevailing winds. The storage battery has 
been suggested as a feasible means of supply- 
ing this power, but the storage battery is even 
less efficient in proportion to its weight than 
the steam engine, to say nothing, of the prac- 
tical difficulties in the way of recharging it 
with energy. 
As far as we can now foresee, the railroad 
will always remain our best means of loco- 
motion. Undoubtedly immense impro\e- 
ments will be made in our present system, 
as regards safety, comfort, speed, and econ- 
omy ; and, although the traveller of a hundred 
years hence may, very likely, look- back upon 
our limited expresses as something only fit 
for emigrants, yet we are inclined to believe 
that the fiuidamental tvpe of the railroad will 
always persist, and that as long as the human 
race remains upon the earth it must confine 
itself in its movements to the surface of the 
land and water. 
[Original in Popular Science News.} 
ALUMINIUM. 
BY GEORGE L. BURDITT. 
One of the most abundant elements on earth — 
in fact, the most abundant metal — is aluminium. It 
occurs in combination with oxygen and silicon, and 
is the principal basic radical in many minerals, 
such as slate, feldspar, and mica. It occurs in clay, 
marl, and in different soils; also in sapphires, 
■■ubies, and emeralds. In all, about one-twelfth of 
the earth is aluminium. 
Many aluminium salts had been known from 
early times, and had been utilized in different ways, 
but the pure metal had not been known. It was 
first obtained by Wohler, in the form of steel gray 
powder, but afterwards in malleable globules. 
Others have obtained it by heating metallic sodium 
with chloride or fluoride of aluminium, or with a 
double chloride or fluoride of aluminium and 
sodium. 
The pure metal (AI2V1, 27) is bluish-white, with 
a bright metallic lustre. Its low specific gravity 
(2.56) is its most remarkable property. It is duc- 
tile, malleable, and tenacious, and may be rolled 
into sheets or drawn into fine wire. It melts at 
about 700°. It conducts heat better than silver, 
and electricity better than iron. It 4s permanent in 
air, melts slowly when heated, and crystallizes in 
octahedrons on cooling. When melted in a cruci- 
ble, it does not oxidize, and so it may be cast. 
When dropped or struck, it gives a clear, musical 
note, but is too sonorous for bells. Neither concen- 
trated nor dilute nitric acid acts upon it, but it is 
readily attacked by both concentrated and dilute 
hydrochloric acid. 
The uses of aluminium are, at. present, compara- 
tively few, owing to its cost and the difficulty with 
which it is prepared. It is used chiefly on philo- 
sophical instruments where permanence, lightness, 
and rigidity are needed. For the same reason, it is 
beginning to replace copper in making scale-beams 
for delicate balances, being only about one-fourth 
as heavy as copper, and of about the same rigidity. 
Small weights are also made of it. Owing to its 
permanence, it is used sometimes for cap-stones. 
The cap-stone of the Washington Monument is of 
aluminium, and is said to be the largest piece in 
existence. 
Aluminium forms a number of interesting com- 
pounds. It readily unites with copper, silver, and 
iron to form alloys. It may be melted with lead, 
however, and no combination will take place. The 
alloy with copper is a golden yellow, and takes a 
high polish. It is much used as jewelry, being the 
best imitation of gold. Aluminium treated with 
sodic hydrate gives the rough, frosty surface lately 
so popular on jewelry. Messrs. Bell manufac- 
ture a yellow alloy containing ten per cent, of 
alurninium, which they call aluminium bronze. It 
