In 1886 he left the public service to work as a prospector, spending time on the Teetulpa and Mannahill goldfields and in the Barrier Ranges of New South Wales.

[3] He soon moved to the north-west to participate in the Pilbara goldrush, remaining in the district for eight years where he managed the Stray Shot, Excelsior, Augusta, and Talga-Talga mines.

He moved to Sydney after his election to the Senate and died of a coronary occlusion at his home in Elizabeth Bay on 15 January 1935, aged 70.

[4] Kingsmill served two terms as president of the Lawn Tennis Association of Western Australia and was voted a life member.

He was the president of the board of Perth Zoo from 1916 to 1922 and acting director from 1916 to 1917, during which time he travelled to Singapore and the Federated Malay States to buy animals.