Traveller on Family Tree Circles

My grandmother - born Jane Turnbull in 1879 in Carlisle, England - always said that two of her uncles had emigrated to Australia but despite a lot of searching I can find no trace of them. I believe the two uncles were William Turnbull born 1862 in Wigton, Cumberland, England, and John Turnbull, born 1866 in Carlisle, Cumberland, England. Both can be found in the 1891 census but are missing from future census records. This would indicate they moved to Australia in the 1890s. It is possible that both men were members of the Salvation Army. I would welcome any suggestions on how I might find them. William Lowther.