"i.g." is Io-gallic paper.  Talbot's entry for 1 September 1842 in his 'Notebooks Q' stated, "Wash Iodized paper with solution of gallic acid in water and dry it."  Io-gallic paper became part of Talbot's 1843 Patent No. 9753, 'Improvements in Photography', where Talbot noted that Io-gallic paper differed from the calotype process in that it could be prepared in advance and stored away from light until required which would have been useful in field work.