Note 53 — PART I SPECIFICATIONS FOR STREET ROADWAY PAVEMENTS (continued 2)

Most of the more recent specifications require the use of a heavy oil, said to be composed of creosote oil with an admixture of refined tar, on the ground that the tar is necessary as a water-proofing agent to prevent the creosote oil from being dissolved out by water or evaporated into the air. It is claimed that if moisture can thus be excluded from entering the wood, decay will be prevented, even in the absence of the antiseptic elements of creosote oil. It is not intended to discuss this matter at length here. We know from long experience that genuine creosote oil is the best preservative of wood so far found; also that creosoted piles have stood in tidal waters, alternately exposed to water and air, for twenty-five years and still retain sufficient creosote oil to resist the Teredo—a very severe test. Why experiment with a comparatively untried material, particularly when it costs as much as the genuine creosote oil, is rather more difficult to force into the wood, and has some admitted objectionable qualities?