ts of the tar,
which still remain unaltered, are exposed to the action of the oxygen,
but also the fibers of the roofing paper are exposed to decomposition.
How destructive the alternating influence of the oxygen and the
atmospheric precipitations are for the roofing paper will be shown by
the following results of tests. It will have been observed that the
rain water running from an old paper roof, especially after dry
weather, has a yellowish, sometimes a brown yellow color. The
supposition that this colored rain water might contain decomposition
products of the roofing paper readily prompted itself, and it has been
collected and analyzed at different seasons of the year. After a
period of several weeks of fair weather during the summer, rain fell,
and the sample of water running from a roof was caught and evaporated;
the residue when dried weighed 1.68 grammes. It was of a brownish
black color, fusible in heat and readily soluble, with a yellow brown
color in water. The dark brown substance readily dissolved in ammonia,
alcohol, dilute acid, hydrochloric acid, sulphuric acid, and
decomposed in nitric acid, but did not dissolve in benzine or fat oil.
After several days' rain during the summer, a quantity of the water
was caught, evaporated, and the residue dried. Its characteristics
were similar to those above mentioned. By an experiment instituted in
water under conditions similar to the first mentioned, the dry brown
substance weighed 71 grammes. It possessed the same characteristics.
In the solution effected with water containing some aqua ammonia of
the brown substance, a white precipitate of oxalate of lime occurred
when an oxalate of ammonia solution was added, but the brown substance
remained in solution. A further precipitation of oxalate of lime was
produced by a solution of oxalic acid, but the brown organic substance
remained in solution. This organic substance being liberated from the
lime was evaporated, and left a dry, resinous, fusible brownish black
substance, which also dissolved readily in water. It will be seen from
these trials that the substance obtained from the rain water running
from a paper roof is a combination of an organic acid with lime, which
readily dissolves in water, and that also the free organic acid
combined with the lime dissolves easily in water.

The question concerning the origin of this organic substance or its
combination with lime can only be answered in one way, viz., that it