In India, Valentine played an important role in improving the health and society of the regions of Mewar and Jeypore.
He started weaving on the handloom at an early age, but his failing health forced his parents to focus instead on his education.
Thus, as a child, Valentine thought much about death and eagerly read books about heaven, his favorite being "The World to Come" by Isaac Watts.
After Valentine’s grandfather died, his grandmother let a few boarders stay at their house, most notably politicians and great readers.
Valentine returned to Brechin, and began preaching and holding prayer meetings in a small vacant school under the Free Church.
Upon completion of his studies, Valentine was appointed by the United Presbyterian Mission Board as a medical missionary to India.
[citation needed] The United Presbyterian Church resolved to establish a mission in India in 1858, and chose Rajputana as its location.
As he and Dr. Shoolbred visited the surrounding villages and prescribed medications, they were able to gain the trust of these communities through their success in treating patients.
[4] In addition to the surrounding villages, Valentine and the other missionaries visited Nusserabad, Ajmere, Pokhur, and the native state of Kiehneghur.
In 1862, Valentine, along with Shoolbred and Robson, wrote to the superintendent requesting permission to use a building that once was a dispensary in the city of Aya Nagar.
The superintendent posted notices around the city, which led to meetings held by Brahmans and Bunyas (merchants) that concluded in their decision to bar anyone from going to the dispensary.
When he successfully supported the Bunya through the infection, the city rejoiced, and patients then came to the dispensary to receive the mission's services.
[3] With his interest in education in addition to medicine, Valentine examined the schools established by the government and found them to be in poor condition.
[13] While in Jeypore, Valentine remained close to the Maharaja, which permitted him to establish several institutions, including a School of Arts, a Public Library, a Philosophical Institute, a Museum, a Medical Hall, branch dispensaries, a board of health, and to enact prison reform.
[16] In May 1875, Valentine's work in Jeypore was recognized by the Foreign Mission Board of the United Presbyterian Church.
Its objectives were to serve as a boarding house for native Christian medical students, to prepare for and/or supplement their education in the Government School of Medicine, to educate them about the Bible and in systematic theology, and to strengthen their public speaking skills by providing them with opportunities to preach to Christian and non-Christian audiences.
[17] A Calcutta newspaper called the Indian Witness reported on 27 October 1883 that women were currently attending the Agra Medical Missionary Training Institution through scholarships from the government.
The institution itself proposed to provide scholarships for male and female students who wished to pursue medical training in Agra.
One such example is that of a Hindu widow who was accepted into the Institution, graduated at the top of her class, and received a Lady Ripon Scholarship.
[15] Graduates from the Institution went off to do medical missionary work in various places, including John Brand in Jodhpur, Saul David in Delhi, Henry Phillips in Agra, Newel Kishore in Nasirabad, Puran Lal in Ujjain, Ahmad Shah in Rutlam, Ghasa Singh in Bulandshahar, Thomas Solomon in Beluchistan, Henry Theophilus in Ajmere, and Samuel Masih in Neemuch.
[13] In 1905, Valentine began an endowment of 1,000 rupees in the Foreign Mission Board of the United Presbyterian Church for scholarships to students.
[19] Two female English medical missionaries, Dr. Edith Brown and Miss Greenfield, were influenced by Valentine’s Agra Institution and founded the North India School of Medicine for Christian Women at Ludhiana in the Punjab in the autumn of 1894.