Scientific American Supplement, No. 821, Sep. 26, 1891 written by Various
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Various >> Scientific American Supplement, No. 821, Sep. 26, 1891
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SCIENTIFIC AMERICAN SUPPLEMENT NO. 821
NEW YORK, September 26, 1891
Scientific American Supplement. Vol. XXXII, No. 821.
Scientific American established 1845
Scientific American Supplement, $5 a year.
Scientific American and Supplement, $7 a year.
* * * * *
TABLE OF CONTENTS.
I. Architectural.--The New Labor Exchange in Paris.--With
views of the interior and exterior of the building
II. Electrical.--The Construction and Maintenance of Underground
Circuits.--By S.B. FOWLER.--A comprehensive article,
discussing at length the various devices for protecting underground
circuits, methods _of_ inserting the cables, etc.
III. Engineering.--Railroads to the Clouds.--Sketches of a number
of mountain railroads
IV. Marine Engineering.--The French Armored Turret Ship
the Marceau.--1 engraving.--A full description of the vessel, giving
dimensions and cost
A Review of Marine Engineering during the Past Decade.--A
paper read before the Institution of Mechanical Engineers by Mr.
Alfred Blechynben, of Barrow-in-Furness.--This paper, which
is continued from Supplement No. 820, treats on steam pipes,
feed water heating, twin screws, etc.
V. Miscellaneous.--The Little House.--An article giving various
hints about the arrangement and management of small
dwellings, with special view to the best sanitary arrangements
Stilt Walking.--A sketch, with engraving, of Sylvain Dornon,
the stilt walker of Landes
Remains of a Roman Villa in England
Gum Arabic and its Modern Substitutes.--A continuation of a
paper by Dr. S. Rideal and W.E. Youle.--With 26 tables
A New Method of Extinguishing Fires.--Invented by George
Dickson and David A. Jones, of Toronto, Canada.--Apparatus designed
to utilize a mixture of water and liquefied carbonic acid
VI. Medicine and Hygiene.--The Hygienic Treatment of
Obesity.--By Dr. Paul Chebon.--Methods of eating, drinking,
and exercising for the purpose of reducing fat.--An extended
article, giving valuable information to people troubled with too
much flesh
VII. Photography.--Spectroscopic Determination of the Sensitiveness
of Dry Plates.--A full description of the new plan of
Mr. G.F. WILLIAMS, for determining the sensitiveness of dry
plates by the use of a small direct vision pocket spectroscope
VIII. Physics.--A Physical Laboratory Indicator.--By J.W.
MOORE, of Lafayette College.--1 engraving.--This is a modification
of the old peg board adapted to use in the laboratory.--It indicates
the names of the members of the class, contains a full
list of the experiments to be performed, refers the student
to the book and page where information in reference to experiments
or apparatus may be found, it shows what experiments
are to be performed by each student at a given time, etc.
Cailletet's Cryogen.--A description, with one engraving, of Mr.
Cailletet's new apparatus for producing temperatures from 70
degrees to 80 degrees C., below zero, through the expansion of
liquid carbonic acid
IX. Technology.--The Manufacture of Roll Tar Paper.--An extended
article containing a historical sketch and full information
as to the materials used and the methods of manufacture
Smokeless Gunpowder.--By Hudson Maxim.--A comprehensive
article on the manufacture and use of smokeless gunpowder,
giving a sketch of its history, and describing the methods of
manufacture and its characteristics
Method of Producing Alcohol.--A description of an improved
process for making alcohol.--Invented by Mr. Alfred Springer,
of Cincinnati, Ohio
* * * * *
[Illustration: INTERIOR OF THE NEW LABOR EXCHANGE, PARIS.]
[Illustration: NEW LABOR EXCHANGE, PARIS.]
THE NEW LABOR EXCHANGE, PARIS.
The new Labor Exchange is soon to be inaugurated. We give herewith a
view of the entrance facade of the meeting hall. The buildings, which
are the work of Mr Bouvard, architect, of the city of Paris, are
comprised within the block of houses whose sharp angle forms upon
Place de la Republique, the intersection of Boulevard Magenta and
Bondy street. One of the entrances of the Exchange is on a level with
this street. The three others are on Chateau d'Eau street, where the
facade of the edifice extends for a length of one hundred feet. From
the facade and above the balcony that projects from the first story,
stand out in bold relief three heads surrounded by foliage and fruit
that dominate the three entrance doors. These sculptures represent the
Republic between Labor and Peace. The windows of the upper stories are
set within nine rows of columns, from between the capitals of which
stand out the names of the manufacturers, inventors, and statesmen
that have sprung from the laboring classes. Upon the same line, at the
two extremities of the facade, two modillions, traversed through their
center by palms, bear the devices "Labor" and "Peace." Above, there is
a dial surmounted by a shield bearing the device of the city of Paris.
The central door of the ground floor opens upon a large vestibule,
around which are arranged symmetrically the post, telegraph,
telephone, and intelligence offices, etc. Beyond the vestibule there
is a gallery that leads to the central court, upon the site of which
has been erected the grand assembly hall. This latter, which measures
20 meters in length, 22 in width, and 6 in height, is lighted by a
glazed ceiling, and contains ten rows of benches. These latter contain
900 seats, arranged in the form of circular steps, radiating around
the president's platform, which is one meter in height. A special
combination will permit of increasing the number of seats reserved for
the labor associations on occasions of grand reunions to 1,200. The
oak doors forming the lateral bays of the hall will open upon the two
large assembly rooms and the three waiting rooms constructed around
the faces of the large hall. In the assembly rooms forming one with
the central hall will take place the deliberations of the syndic
chambers. The walls of the hall will, ere long, receive decorative
paintings.--_L'Illustration._
* * * * *
MANUFACTURE OF ROLL TAR PAPER.
Roofing paper was first used in Scandinavia early as the last century,
the invention being accredited to Faxa, an official of the Swedish
Admiralty. The first tar and gravel roofs in Sweden were very
defective. The impregnation of the paper with a water-proofing liquid
had not been thought of, and the roofs were constructed by laying over
the rafters a boarding, upon which the unsaturated paper, the sides of
which lapped over the other, was fastened with short tacks. The
surface of the paper was next coated with heated pine tar to make it
waterproof. The thin layer of tar was soon destroyed by the weather,
so that the paper, swelled by the absorption of rain water, lost its
cohesiveness and was soon destroyed by the elements. This imperfect
method of roof covering found no great favor and was but seldom
employed.
In Germany the architect Gilly was first to become interested in tar
paper roofing, and recommended it in his architecture for the country.
Nevertheless the new style of roof covering was but little employed,
and was finally abandoned during the first year of the 19th century.
It was revived again in 1840, when people began to take a renewed
interest in tar paper roofs, the method of manufacturing an
impermeable paper being already so far perfected that the squares of
paper were dipped in tar until thoroughly saturated. The roof
constructed of these waterproof paper sheets proved itself to be a
durable covering, being unimpenetrable to atmospheric precipitations,
and soon several factories commenced manufacturing the paper. The
product was improved continually and its method of manufacture
perfected. The good qualities of tar paper roofs being recognized by
the public, they were gradually adopted. The costly pine tar was soon
replaced by the cheaper coal tar. Square sheets of paper were made at
first; they were dipped sufficiently long in ordinary heated coal tar,
until perfectly saturated. The excess of tar was then permitted to
drip off, and the sheets were dried in the air. The improvement of
passing them through rollers to get rid of the surplus tar was
reserved for a future time, when an enterprising manufacturer
commenced to make endless tar paper in place of sheets. Special
apparatus were constructed to impregnate these rolls with tar; they
were imperfect at first, but gradually improved to a high degree. Much
progress was also made in the construction of the roofs, and several
methods of covering were devised. The defects caused by the old method
of nailing the tar paper direct upon the roof boarding were corrected;
the consequence of this method was that the paper was apt to tear,
caused by the unequal expansion of the roofing boards and paper, and
this soon led to the idea of making the latter independent of the
former by nailing the sides of the paper upon strips running parallel
with the gable. The use of endless tar paper proved to be an essential
advantage, because the number of seams as well as places where it had
to be nailed to the roof boarding was largely decreased. The
manufacture of tar paper has remained at about the same stage and no
essential improvements have been made up to the present. As partial
improvement may be mentioned the preparation of tar, especially since
the introduction of the tar distillery, and the manufacture of special
roof lacquers, which have been used for coating in place of the coal
tar. As an essential progress in the tar paper roofing may be
mentioned the invention of the double tar paper roof, and the wood
cement roof, which is regarded as an offshoot.
The tar paper industry has, within the last forty years, assumed great
dimensions, and the preferences for this roofing are gaining ground
daily. In view of the small weight of the covering material, the wood
construction of the roof can be much lighter, and the building is
therefore less strained by the weight of the roof than one with the
other kind, so that the outer walls need not be as heavy. Considering
the price, the paper roof is not only cheaper than other fireproof
roofs, but its light weight makes it possible for the whole building
to be constructed lighter and cheaper. The durability of the tar paper
roof is satisfactory, if carefully made of good material; the double
tar paper roof, the gravel double roof, and the wood cement roof are
distinguished by their great durability.
These roofs may be used for all kinds of buildings, and not only are
factories, storehouses, and country buildings covered with it, but
also many dwellings. The most stylish residences and villas are at
present being inclosed with the more durable kinds; the double roof,
the gravel double roof, and the wood cement roof. For factory
buildings, which are constantly shaken by the vibrations of the
machinery, the tar paper roof is preferable to any other.
In order to ascertain to what degree tar paper roofs would resist
fire, experiments were instituted at the instigation of some of the
larger manufacturers of roofing paper, in the presence of experts,
architects, and others, embracing the most severe tests, and it was
fully proved that the tar paper roof is as fireproof as any other.
These experiments were made in two different ways; first, the
readiness of ignition of the tar paper roof by a spark or flame from
the outside was considered, and, second, it was tested in how far it
would resist a fire in the interior of the building. In the former
case, it was ascertained that a bright, intense fire could be kept
burning upon the roof for some time, without igniting the woodwork of
the roof, but heat from above caused some of the more volatile
constituents of the tar to be expelled, whereby small flames appeared
upon the surface within the limits of the fire; the roofing paper was
not completely destroyed. There always remained a cohesive substance,
although it was charred and friable, which by reason of its bad
conductivity of heat protected the roof boarding to such an extent
that it was "browned" only by the developed tar vapors. A fire was
next started within a building covered with a tar paper roof; the
flame touched the roof boarding, which partly commenced to char and
smoulder, but the bright burning of the wood was prevented by the
air-tight condition of the roof; the fire gases could not escape from
the building. The smoke collecting under the roof prevented the
entrance of fresh air, in consequence of which the want of oxygen
smothered the fire. The roofing paper remained unchanged. By making
openings in the sides of the building so that the fire gases could
escape, the wood part of the roof was consumed, but the roofing paper
itself was only charred and did not burn. After removing the fire in
contact with the paper, this ceased burning at once and evinced no
disposition whatever to spread. In large conflagrations, also, the tar
paper roofs behaved in identically a similar manner. Many instances
have occurred where the tar paper roof prevented the fire from
spreading inside the building, and developing with sufficient
intensity to work injury.
As it is of interest to the roofer to know the manner of making the
material he uses, we give in the following a short description of the
manufacture of roofing paper. At first, when square sheets were used
exclusively, the raw paper consisted of ordinary dipped or formed
sheets. The materials used in its manufacture were common woolen rags
and other material. In order to prepare the pulp from the rags it is
necessary to cut them so small that the fabric is entirely dissolved
and converted into short fibers. The rags are for this purpose first
cut into pieces, which are again reduced by special machines. The rags
are cut in a rag cutting machine, which was formerly constructed
similar to a feed cutter; later on, more complicated machines of
various constructions were employed. It is not our task to describe
the various kinds, but we remain content with the general remark that
they are all based on the principles of causing revolving knives to
operate upon the rags. The careful cleansing of the cut rags,
necessary for the manufacture of paper, is not required for roofing
paper. It is sufficient to rinse away the sand and other solid
extraneous matter. The further reduction of the cut rags was formerly
performed in a stamp mill, which is no longer employed, the pulp mill
or rag engine being universally used.
The construction of this engine may be described as follows: A box or
trough of wood, iron, or stone is by a partition divided into two
parts which are connected at their ends. At one side upon the bottom
of the box lies an oakwood block, called the back fall. In a hollow of
this back fall is sunk the so-called plate, furnished with a number of
sharp steel cutters or knives, lying alongside of each other. A roller
of solid oakwood, the circumference of which is also furnished with
sharp steel cutters or knives, is fastened upon a shaft and revolves
within the hollow. The journal bearings of the shaft are let into and
fastened in movable wooden carriers. The carriers of the bearings may
be raised and lowered by turning suitable thumbscrews, whereby the
distance between the roller and the back fall is increased or
decreased. The whole is above covered with a dome, the so-called case,
to prevent the throwing out of the mass under the operation of
grinding. The roller is revolved with a velocity of from 100 to 150
revolutions per minute, whereby the rags are sucked in between the
roller and the back fall and cut and torn between the knives. At the
beginning of the operation, the distance between the roller and the
back fall is made as great as possible, the intention being less to
cut the rags than to wash them thoroughly. The dirty water is then
drawn off and replaced by clean, and the space of the grinding
apparatus is lessened gradually, so as to cut the rags between the
knives. The mass is constantly kept in motion and each piece of rag
passes repeatedly between the knives. The case protects the mass from
being thrown out by the centrifugal force. The work of beating the
rags is ended in a few hours, and the ensuing thin paste is drawn off
into the pulp chest, this being a square box lined with lead.
From the pulp chest it passes to the form of the paper machine. This
form consists of an endless fine web of brass wire, which revolves
around rollers. The upper part of this form rests upon a number of
hollow copper rollers, whereby a level place is formed. The form
revolves uniformly around the two end rollers, and has at the same
time a vibratory motion, by which the pulp running upon the form is
spread out uniformly and conducted along, more flowing on as the
latter progresses. The water escapes rapidly through the close wire
web. In order to limit the form on the sides two endless leather
straps revolve around the rollers on each side, which touch with their
lower parts the form on both sides and confine the fluid within a
proper breadth. The thickness of the pulp is regulated at the head of
the form by a brass rule standing at a certain height; its function is
to level the pulp and distribute it at a certain thickness. The
continually moving pulp layer assumes greater consistency the nearer
it approaches to the dandy roll. This is a cylinder covered with brass
wire, and is for the purpose of compressing the paper, after it has
left the form, and free it from a great part of the water, which
escapes into a box. The paper is now freed of a good deal of the
fluid, and assumes a consistency with which it is enabled to leave the
form, which now commences to return underneath the paper, passing on
to an endless felt, which revolves around rollers and delivers it to
two iron rolls. The paper passes through a second pair of iron
rollers, the interiors of which are heated by steam. These rollers
cause the last of the water to be evaporated, so that it can then be
rolled upon reels. A special arrangement shaves the edges to the exact
size required.
The paper is made in different thicknesses and designated by numbers
to the size and weight.
Waste paper, bookbinders' shavings, etc., can be used for making the
paper. As much wool as possible should be employed, because the wool
fiber has a greater resistance than vegetable fiber to the effects of
the temperature. By wool fiber is understood the horny substance
resembling hair, with the difference that the former has no marrowy
tissue. The covering pellicle of the wool fiber consists of flat,
mostly elongated leaves, with more or less corners, lying over each
other like scales, which makes the surface of the fiber rough; this
condition, together with the inclination of curling, renders it
capable of felting readily. Pure wool consists of a horny substance,
containing both nitrogen and sulphur, and dissolves in a potash
solution. In a clean condition, the wool contains from 0.3 to 0.5 per
cent. of ash. It is very hygroscopical, and under ordinary
circumstances it contains from 13 to 16 per cent. humidity, in dry air
from 7 to 11 per cent., which can be entirely expelled at a
temperature of from 226 to 230 degrees Fahrenheit. Wool when ignited
does not burn with a bright flame, as vegetable fiber does, but
consumes with a feeble smouldering glow, soon extinguishes, spreading
a disagreeable pungent vapor, as of burning horn. By placing a test
tube with a solution of five parts caustic potash in 100 parts water,
a mixture of vegetable fibers and wool fibers, the latter dissolve if
the fluid is brought to boiling above an alcohol flame, while the
cotton and linen fibers remain intact.
The solubility of the woolen fibers in potash lye is a ready means of
ascertaining the percentage of wool fiber in the paper. An exhaustive
analysis of the latter can be performed in the following manner: A
known quantity of the paper is slowly dried in a drying apparatus at
temperature of 230 deg. Fahrenheit, until a sample weighed on a scale
remains constant. The loss of weight indicates the degree of humidity.
To determine the ash percentage, the sample is placed in a platinum
crucible, and held over a lamp until all the organic matter is burned
out and the ash has assumed a light color. The cold ash is then
moistened with a carbonate of ammonia solution, and the crucible again
exposed until it is dark red; the weight of the ash is then taken. To
determine the percentage of wool, a sample of the paper is dried at
230 deg. Fahrenheit and weighed, boiled in a porcelain dish in potash lye
12 deg. B. strong, and frequently stirred with a glass rod. The wool fiber
soon dissolves in the potash lye, while the vegetable fiber remains
unaltered. The pulpy mass resulting is placed upon a filter, dried at
212 deg. Fahrenheit, and after the potash lye has dripped off, the
residue, consisting of vegetable fiber and earthy ash ingredients, is
washed until the water ceases to dissolve anything. The residue dried
at 212 deg. Fahrenheit is weighed with a filter, after which that of the
latter is deducted. The loss of weight experienced is essentially
equal to the loss of the wool fiber. If the filtrate is saturated with
hydrochloric acid, the dissolved wool fiber separates again, and after
having been collected upon a weighed filter, it may be weighed and the
quantity ascertained.
The weight of the mineral substances in the raw paper is ascertained
by analyzing the ash in a manner similar to that above described. The
several constituents of the ash and the mineral added to the raw paper
are ascertained as follows: Sufficient of the paper is calcined in the
manner described; a known quantity of the ash is weighed and thrown
into a small porcelain dish containing a little distilled water and an
excess of chemically pure hydrochloric acid. In this solution are
dissolved the carbonates, carbonate of lime, carbonate of magnesia, a
little of sulphate of alumina, as well as metallic oxides, while
silicate of magnesia, silicic acid, sulphate of lime (gypsum) remain
undissolved. The substance is heated until the water and excess of
free hydrochloric acid have been driven off; it is then moistened with
a little hydrochloric acid, diluted with distilled water and heated.
The undissolved residue is by filtering separated from the dissolved,
the filter washed with distilled water, and the wash water added to
the filtrate. The undissolved residue is dried, and after the filter
has also been burned in due manner and the ash added, the weight is
ascertained. It consists of clay, sand, silicic acid and gypsum.
The filtrate is then poured into a cylinder capable of holding 100
cubic centimeters, and furnished with a scale; sufficient distilled
water is then added until the well-shaken fluid measures precisely 100
cubic centimeters. By means of this measuring instrument, the filtrate
is then divided into two equal portions. One of these parts is in a
beaker glass over-saturated with chemically pure chloride of ammonia,
whereby any iron of oxide present and a little dissolved alumina fall
down as deposit. The precipitate is separated by filtering, washed,
dried at 212 deg. Fahrenheit and weighed. To the filtrate is then added a
solution of oxalate of ammonia until a white precipitate of oxalate of
lime is formed. This precipitate is separated by filtering, washed,
dried and when separated from the filter, is collected upon dark
satinized paper; the filter itself is burned and the ash added to the
oxalate of lime. This oxalate of lime is then heated to a dark red
heat in a platinum crucible with lid until the oxalate of lime is
converted into carbonate of lime. By the addition of a few drops of
carbonate of ammonia solution and another slight heating of the
crucible, also the caustic lime produced in the filter ash by heating,
is reconverted into carbonate of lime, and after cooling in the
exsiccator, the whole contents of the crucible is weighed as
carbonate of lime, after deducting the known quantity of filter ash.
Any magnesia present in the filtrate of the oxalate of lime is by the
addition of a solution of phosphate of soda separated as phosphate of
ammonia and magnesia, after having stood twenty-four hours. The
precipitate is filtered off, washed with water to which a little
chloride of ammonia is added, dried, and after calcining the fiber and
adding the filter ash, glow heated in the crucible. The glowed
substance is weighed after cooling, and is pyrophosphate of magnesia,
from which the magnesia or carbonate of magnesia is calculated
stoichiometrically. All the ascertained sums must be multiplied by 2,
if they are to correspond to the analyzed and weighed quantity of ash.
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