People knew for centuries there was this sludge underground, but did they know what it really was or did they have any uses for it until the late nineteen century when engines were invented? How historically was crude oil/petroleum viewed as or thought to be?
Hi, while you're waiting for responses here, you might be interested in some earlier threads
[How was oil obtained in the Middle Ages?] (https://www.reddit.com/r/AskHistorians/comments/26lpwy/how_was_oil_obtained_in_the_middle_ages) featuring /u/JebusGobson and a link to the FAQ
Someone told me that the Chinese used natural gas. Is this correct? featuring /u/Vinar