uence 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, an