1299. 'They had bitumen for clay' means that they had evil springing from evil desire in place of good. This is clear from the meaning in the Word of 'bitumen' and of 'clay'. Since the subject here is the building of the tower of Babel, the materials mentioned are such as are used in building. Bitumen is mentioned because of its sulphurous and combustible qualities, which in the Word mean evil desires, chiefly those that belong to self-love. Here 'bitumen' means the evils springing from evil desires, as well as the resulting falsities, as these too are the evils from which the tower described below was constructed. That such things are meant is clear in Isaiah,

The day of Jehovah's vengeance - her streams will be turned into pitch, and her dust into sulphur; and her land will become burning pitch. Isaiah 34:8-9.

'Pitch' and 'sulphur' stand for falsities and evils that spring from evil desires. And there are further examples besides these.