BITUMEN, the name applied by the Romans to the various descriptions of natural hydrocarbons, the word petroleum not being used in classical Latin. In its widest sense it embraces the whole range of these substances, including natural gas, the more or less liquid descriptions of petroleum, and the solid forms of asphalt, albertite, gilsonite or uintahite, elaterite, ozokerite and hatchettite. To distinguish bitumen intermediate in consistency between asphalt and the more liquid kinds of crude petroleum, the term maltha (Latin) is frequently employed. The bitumens of chief commercial importance may be grouped under the three headings of (1) natural gas, (2) petroleum, and (3) asphalt, and will be found fully described under these titles. In the scriptures there are numerous references to bitumen, among which the following may be quoted:—In Genesis ix. 3, we are told that in the building of the tower of Babel “slime had they for mortar,” and in Genesis xiv. 10, that the vale of Siddim “was full of slime-pits,” the word slime in the latter quotation from our version appearing as bitumen in the Vulgate. Herodotus alludes to the use of the bitumen brought down by the Is, a tributary of the Euphrates, as mortar in building the walls of Babylon. Diodorus, Curtius, Josephus, Bochart and others make similar mention of this use of bitumen, and Vitruvius tells us that it was employed in admixture with clay.
In its various forms, bitumen is one of the most widely distributed of substances. It occurs, though sometimes only in small quantity, in almost every part of the globe, and throughout the whole range of geological strata, from the Laurentian rocks to the most recent members of the Quaternary period. Although the gaseous and liquid forms of bitumen may be regarded as having been formed in the strata in which they are found or as having been received into such strata shortly after formation, the semi-solid and solid varieties may be considered to have been produced by the oxidation and evaporation of liquid petroleum escaping from underlying or better preserved deposits into other strata, or into fissures where atmospheric action and loss of the more volatile constituents can take place. It should, however, be stated that there is some difference of opinion as to the precise manner of production of some of the solid forms of bitumen, and especially of ozokerite. (B. R.)