The letters reflect the fact that the correspondence took place during Joseph Needham's 1958 tour of Ceylon, Singapore, Thailand and China. The correspondence comprises 9 letters from Ho; copies of 3 letters from Needham to Ho; copy of 1 letter from Needham to Prof. A. Oppenheim of the University of Malaya, Singapore, about Ho's work. Other matters discussed include sources of Japanese and Korean astronomical records in Cambridge University Library; useful people to meet in Singapore; Ho's plans for further study in England; Taoist alchemical texts; Tun Huang [敦煌 / Dun Huang] manuscripts; 《三十六水法》 [San Shih Liu Shui Fa / San Shi Liu Shui Fa].