Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he gives advice on when to send plants as the current specimens were all dead when he retrieved them from the Custom House. He writes of jealousy among the Directors of India House if plants arrive for private persons and so therefore asks Wallich to send specimens to them but to continue to send him seeds. He adds thanks for geological specimens and for Wallich to forward letters of acknowledgement to General Hardwick and Dr Adams. He asks whether the other gentlemen might be interested in joining the Geological Society. Handwritten, dated 20 January 1820, received 9 July 1820.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he discusses the possibility of the introduction of rice to England. Colebrooke thanks for letters, boxes of specimens and anthropological drawings. Colebrooke asks Wallich to express his thanks to the gentlemen that provided geological specimens. Colebrooke has petitioned the Chair of the Court of Directors, East India Company on Wallich's behalf. He wishes Wallich a speedy recovery to health. Handwritten, dated 8 August 1820, received 25 February 1821.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich acknowledging letters sent and stating that he has sorted Wallich's remittances and arranged for the periodicals he requests to be sent to him. He was pleased with the geological specimens sent to him, including gold from Tartary and specimens from Lieutenant Gerard and Mr Scott and Colebrooke has used the notes sent by Gerard to write a paper on the geology of the valley of the Sutlej. He has proposed Lt Gerard and Dr Jack as members of the Geological Society. He thanks Wallich for seeds sent but advises because of the cost to be careful in thinking through which to send. Handwritten, dated 9 January 1821, received 5 June 1821.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he writes concerning the high cost of importing specimens. He therefore asks that they are no longer sent to him individually but to send seeds to other sources who have requested them and geological specimens direct to the Geological Society. Mr Scott, Dr Jack and Lt Gerard have all been made members of the Geological Society. Handwritten, dated 22 February 1821, received 14 July 1821.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich concerning publications that Colebrooke will forward to Wallich. He reiterates his request to send specimens direct to the Geological Society because of the cost incurred at the Custom House. Handwritten, dated 12 March 1821, received 30 August 1821.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich to ask Wallich whether he would like the earlier volumes of the Geological Transactions to complete his set as they are available at modest terms. Colebrooke and Mr Lambert have had an interview to request an assistant for Wallich but, as yet, do not know the outcome. The specimens that Wallich sent are still undistributed and therefore Colebrooke suggests that Wallich apportions them to men of science in future. In a postscript Colebrooke mentions that Richardson is still sending publications to Wallich. Handwritten, dated 30 March 1824, received 29 September 1824.

Letter from Henry Thomas Colebrooke to Nathaniel Wallich in which he describes the measures that he has taken to obtain an assistant for Wallich. He regrets the delay in Wallich receiving his publications. He remarks on geological specimens and asks Wallich to thank Capt. G. for the vocabulary of the Kunawar language and is unsure whether to deposit it in the Company's Library or that of the Royal Asiatic Society. He discusses his forestry plantations and the possibility of Wallich obtaining leave. He appends a memo concerning geological specimens. Handwritten, dated 27 July 1825, received 10 December 1825.