Scientific American Supplement, No. 821 | Page 2

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,