Thanks for those links.
No nearer to finding why Samuel left his wife.
It is interesting that Samuel Newton's (1871) mother was an Ivey because it appears that Gertrude's sister Frances(1872) was living with a family named Ivey in 1891 at Gwinear.
Gertrude and Frances parents left Cornwall and died out of County,leaving Frances to return to Cornwall to live with her aunt and uncle.