Rey's career as a mountain guide did not begin until the great age of conquest of the Alps was over. Unlike many of his contemporaries, he did not learn his craft by serving an apprenticeship with other, older guides. One British mountaineer wrote in detail about Rey's achievements in Pioneers of the Alps (1888):His reputation as one of the first rock-climbers in the Alps, and the position he holds among other guides, are the result of his own aptitude and ability, the great enthusiasm he has for his profession, and the energy and earnestness with which he pursues it.