[1][3] Mason's qualifications and experience in bacteriology, public health and law, as well as having the confidence of his colleagues made him qualified for the position.

[3] He appointed six provincial medical officers of health, including Thomas Valintine and Robert Haldane Makgill.

[3] Mason was responsible for reviving the New Zealand Medical Journal which had not been published for four years when he became editor in 1900.

[3] In 1905 Mason contracted diphtheria and handed over to his assistant Chief Health Officer Thomas Valintine.

[4] During World War I Mason served as a bacteriologist on the hospital ship SS Marama.