From The Standard ( London, England ), Thursday, April 10, 1851; Issue 8319.   DEATH. On the 9th inst., at his residence, in St. George's-place, Canterbury, Robert SMITHSON , Esq., proprietor of the Kentish Gazette newspaper, in the 83d year of his age.  He was a collateral descendant of the Yorkshire family of SMITHSON , of which Sir Hugh SMITHSON was created first Duke of Northumberland.