Letters from Sir William Throckmorton in Paris to Edward Coleman [Colman] many written in sympathetic / invisible ink Letters written in invisible ink, probably orange juice, include D239/M/O/1530, 1533, 1536, 1537, 1539-1541, 1543, 1544-1558,1561-1567, 1570-1574. Some letters are wholly written in invisible ink, and others have a second 'secret' letter in invisible ink written between the lines of a letter in ordinary ink. Nov 1674-Apr 1675