"A good deal of his leisure was now employed in the prosecution of chemical experiments. In one of these experiments... which I have heard of from Dr Black, he discovered that mineral alkali is contained in zeolite. On boiling the gelatinous substance obtained from combining that fossil with muriatic acid, he found that, after evaporation, sea-salt was formed. ...from circumstances... it was earlier than 1772. It is, if I mistake not, the first instance of an alkali being discovered in a stony body."