[f. TAR sb. + MACADAM sb.] A mixed material for making roads, consisting of some kind of broken stone or ironstone slag in a matrix of tar alone, or of tar with some mixture of pitch or creosote.
1873. (April 7) H. Gore, in Trans. Soc. of Engineers, 127. This mixture, which the author calls tar macadam, is better if kept a fortnight or three weeks before being laid on the road.
1882. (June 17) Proc. Assoc. Municipal Engineers, VIII. 91. In Barnsley we have tarred macadam, and the cost of it was 1s. 2d. Ibid., 92. I should have liked to have heard more about the cost of the tar-macadam roads. Ibid. (1883), (Sept. 28), X. 53. Tar macadam for roadways was first introduced in Sheffield.
1909. J. W. Smith, Dustless Roads, i. 10. The macadamised road construction of the future is to be found in the use of tar: that is to say, in what is termed tar macadam.
Hence Tarmac, the registered trade-mark of a kind of tar macadam consisting of iron slag impregnated with tar and creosote. Also attrib.
1903. Trades Mark Jrnl., 1 July, Class 17. Tarmac.
1904. Westm. Gaz., 13 Dec., 4/2. Mr. Montagu suggested the making of all roads … by the Tarmac process.
1905. Times, 1 Aug., 14/2. He suggests that the club … should entirely remake some … stretch of road near London with Tarmac.
