[Footnote 19: On the different sorts of oils and bitumens,
see Dr. Watson's (the present bishop of Llandaff's) Chemical
Essays, vol. iii. essay i., a classic book, the best adapted
to infuse the taste and knowledge of chemistry. The less
perfect ideas of the ancients may be found in Strabo
(Geograph. l. xvi. p. 1078) and Pliny, (Hist. Natur. ii.
108, 109.) Huic (Naphthae) magna cognatio est ignium,
transiliuntque protinus in eam undecunque visam. Of our
travellers I am best pleased with Otter, (tom. i. p. 153,
158.)]