70 
POPULAR SOIEJ^OE KEWS. 
[May, 1S90. 
amorphous phosphorus, unites with it at once 
and ignites. 
The existence of allotropic, or different 
varieties of the same element, is a chemical 
mystery which has never been fully accounted 
for. It is a strong argument in favor of the 
compound nature of the elements, or, at least, 
an indication that the molecules of the ele- 
ments are composed of atoms, and have a more 
or less complicsted structure, like the well- 
known isomeric hydrocarbons, which show 
similar phenomena. We have also some 
reason to believe that many other elements 
may show allotropic modiiications, in their 
compounds, at least, although they have not 
yet been distinguished in their free condition. 
<♦» 
A RECENT INVENTION IN PHOTOG- 
RAPHY. 
Since the invention of the rapid dry plates 
which have made instantaneous photography 
a possibility, many attempts have been made 
to fix the successive positions taken by men 
and animals in their natural inovements, and 
with much success. The best of these photo- 
image, and then passing on to give place to 
the next one. The particulars of the mechan- 
ism are not given in La Nature, from which 
we copy the engraving, but the results as 
shown by it are very fine, and indicate a 
remarkable amount of mechanical skill and 
ingenuity. The figures represent the posi- 
tions taken by a horse and rider as they 
moved past the camera, commencing at the 
upper right-hand corner, and following each 
line from right to left, in a reverse direction 
to the lines of a printed page. If M. Marey's 
apparatus proves to be as practicable as is 
claimed, it will undoubtedly be of great value 
and importance to both science and art. 
TO DETECT METALLIC SILVER IN THE 
PRESENCE OF LEAD. 
As silver and lead ver^ commonly occur in nature 
combiped together in the same mineral substances, 
a more easy, rapid, and correct method for the de- 
tection of the former in the presence of the latter 
than any of those generally adopted in practice has 
for a long time been greatly desired, especially by 
assayers and mineralogists. 
The author, who has spent much of his time in 
graphs have been taken by Mr. Muybridge, 
of San Francisco, who placed a number of 
cameras side by side, so arranged that the 
exposure was made by the man, horse, or 
other animal itself, as it moved past tiiem. 
The results obtained were very remarkable, 
the attitudes caught by the sensitive plate 
being so extraordinary and apparently unnat- 
ural that, without the unimpeachable evidence 
afforded by the photographs, one would have 
been justified in saying that they were entirely 
the result of the artist's imagination. 
M. Marey, of France, has recently invented 
an apparatus by which, with a single camera, 
as many as fifty successive exposures of a 
moving object may be taken in a single 
second. Instead of glass plates, he uses a 
sensitive film, which is rolled from one cylin- 
der to another, stopping in the focus of the 
objective just long enough to receive the 
the determination of naturally occurring argentif- 
erous lead compounds, has attempted to supply such 
a method in the extremely simple one detailed 
below, and he hopes it may prove, in the hands of 
others, as successful as it has invariably been with 
himself. 
When a mineral which contains both ot the 
above metals is heated in the ordinary course of 
blowpipe analysis, on charcoal with fusion mixture, 
(K2C03+Na2C03), in the inner or reducing tiame, it 
yields, as is well known, a malleable metallic lead 
(usually lead-gray in color), which is an alloy of 
silver and lead. The silver is readily detected in 
this alloy by treating it as follows : Place it in an 
evaporating dish and cover it well over with moder- 
ately strong nitric acid, and then boil the liquid till 
the bead or beads dissolve ; next nearly neutralize 
the solution thus obtained, with sodium carbonate, 
in a rough manner, but so that it will remain 
weakly acid after the operation. In. this prepared 
solution now allow to lie for some time two strips — 
one of bright copper, and the other of zinc. The 
lead of the solution soon becomes deposited on the 
zinc, while the silver almost entirely goes to coat 
the copper foil ; lift out the latter, and apply to the 
deposit on it a drop of fairly strong nitric acid, and 
then quickly afterwards a drop of potassium chro- 
mate solution. Or, dip the coated foil into moder- 
ately string nitric acid for an instant, and then into 
a dish containing potassium chromate solution. 
The reddish-brown «iass which forms at once, either 
on the upper or under side of the foil, is a sure indi- 
cation of silver. The deposit on the zinc may be 
treated in the same way, and the lemon-yellow mass 
of lead chromate which results will contrast well 
with the brown incrustation obtained on the copper. 
If no silver is present in the solution, the copper 
foil will scarcely become coated at all when placed 
in it. — A. Johnstone, in Chemical News. 
INDUSTRIAL MEMORANDA. 
Blue Soap, rendering the employment of bluing 
in laundry work unnecessary, is made by incorpo- 
rating with ordinary soap a solution of aniline 
green in strong acetic acid. By the action of the 
alkali of the soap, the green is converted into blue, 
uniformly coloring the mass. 
In the Matter of Railwav.s, Japan appears to 
be going ahead tolerably fast. Considerably over 
1,000 miles are already in operation, while an equal 
quantity are under construction or surveyed, and 
will be open within a year or two from now. The 
projected railways exceed 700 miles in length, with 
a capital exceeding £6,000.000 sterling. 
Scale in Boilers. — It is estimated that the pres- 
ence of i-i6 inch of scale causes a loss of 13 per 
cent, of fuel; 'i of inch, 3S per cent., and % of an 
inch of scale, 60 per cent. The Railway Master 
Mechanics' Association of the United States esti- 
mates that the toss of fuel, extra repairs, etc. , due 
to incrustation, amounts to an average of $750 
for every locomotive in the Western and Middle 
States. 
Incombustible Textiles. — There are many sub- 
stances which have the property of rendering the 
fabrics to which they are applied incombustible, but 
they usually spoil them, either by changing the 
color or stiffening them to such a degree that they 
cannot be used. An easy and safe way of protecting 
curtains and mosquito nets against lire is said to be 
by steeping them in a solution of phosphate of 
ammonia, obtained by mixing Vi a liter of water (i 
pint) with 100 grammes (about 3 ounces) of phos- 
phate. In this way the color and texture remain 
unaltered. 
New Insulating Compound. ^-A new insulatin"- 
compound which finds favor among manufacturers 
of electrical instruments and machinery in France 
consists of one part of Greek pitch and two parts of 
burnt plaster by weight, the latter being pure gvpsum 
raised to a high temperature and plunged in water. 
The mixture, when hot. is a paste, and can be 
applied by a brush or cast in moulds. It is 
amber-colored, and can be turned and polished. 
Its advantage is said to be endurance of great 
heat and moisture without injury to its insulating 
properties. 
Electrical Doors. — An admirablearrangement, 
looking to the quick and safe empyting of the house, 
has just been adopted at the Tremont Theatre in 
Boston. At any time, by simply touching a button 
in any one of the eight handy places in different 
parts of the theatre, seventeen sets of folding doors, 
leading to as many exits, open simultaneously, 
actuated by electrical apparatus. The expense of 
the improvements is said to have been considerable, 
but it is eafe to say that the public will appreciate 
the advantage of being able to take their pleasure 
without any dread of fire and panic. 
