The collection consists primarily of Gyll's manuscript travel journals, ten in number, bound into two quarto volumes. The first volume contains his observations on his travels in Spain, ca. 1826/7 (on 84-sides), returning via Germany. This is followed by his journal, 1827/8, of his travels, in the company of his friend, John Davidson, to Italy, Poland, Russia, Germany, Sweden and Denmark (on 181-sides). Other journals comprise a journey to Portugal, August - September 1834 (32-sides); to Paris and environs, November 1834 - January 1935 (22-sides); a tour in England and Wales, July - August 1835 (17-sides); to Malta, Egypt, and the Greek Islands, August 1836 - January 1837 (95-sides); and a tour of Europe, August 1839 - April 1840 (140-sides). Also included (bound in) is Gyll's diary of his readings, 1829-1831.

A third volume contains copies of Gyll's speeches, 1827-1875.

Additionally, loose, are two letters by the English adventurer John Davidson (1797-1836) to Gyll: one, dated 29 August [1835], when he is leaving England bound for Morocco; the other, dated 8 February 1836 from Morocco, while planning his trip to Timbuktu. He headed out in November, and just six weeks into the desert journey his party was ambushed and Davidson was murdered. There is also a permit for Gyll to leave Mexico, signed by Antonio Lopez de Santa Anna (1794-1876), president of Mexico.