It seems remarkable for a writer whose books were as widely distributed as Moss's were to be so little known. Even his place and date of birth are not recorded. George Armstrong of about the same period is another in the same class. Dr. Ernest Caulfield states that Moss is not in any of the ordinary biographical sources, although he has unearthed some contemporary references to his works, wife and sons. In the 1764 edition of his book, there is a footnote which states that he saw a cesarean section at the infirmary in Edinburgh, and he quotes Dr. Whytt on the cause of the infant's breathing.
Still said that Moss received his earliest medical education from Dr. Henry Bracken from whose teaching he may have been lead to take an interest in children. He was surgeon to the Liverpool Lying-in Charity in 1781; when an inoculation society was founded