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