condition, caused by the volatilization of a part of the constituents of the tar. This alteration is materially assisted by the oxygen of the air, which causes the latter to become resinous and exerts a chemical influence upon them. By the volatilization of the lighter tar oils, pores are generated between the fibers of the roofing paper, into which the air and humidity penetrate. In consequence of the greatly enlarged surface, not only the solid ingredients 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.