Lancashire Birth indexes for the years: 1864
CLARKSON Thomas Little Bolton COLLING LB/48/53

Lancashire Marriage indexes for the years: 1886
CLARKSON John Thomas WILD Mary Elizabeth Blackburn, St Peter Blackburn CE136/3/387
CLARKSON Thomas SMITH Mary Blackburn Register Office or Registrar Attended Blackburn RM/95/11

Two possible Marys, but the births of the children show the maiden name as Smith (on Lancashire BMD).

Lancashire Death indexes for the years: 1887
CLARKSON Sarah 0 Witton Blackburn W/20/1

Lancashire Birth indexes for the years: 1888
CLARKSON Elizabeth Witton Blackburn SMITH W/33/83

Lancashire Birth indexes for the years: 1892
CLARKSON Ethel Blackburn Northern Blackburn SMITH BN/27/91

Lancashire Birth indexes for the years: 1894
CLARKSON Sarah Witton Blackburn SMITH W/39/77

Lancashire Birth indexes for the years: 1896
CLARKSON Mary Alice Witton Blackburn SMITH W/41/65

Lancashire Death indexes for the years: 1896
CLARKSON Mary Alice 0 Witton Blackburn W/25/22

Lancashire Birth indexes for the years: 1899
CLARKSON Alice Witton Blackburn SMITH W/45/72

Lancashire Death indexes for the years: 1899
CLARKSON Alice 0 Witton Blackburn W/27/64

Lancashire Birth indexes for the years: 1903
CLARKSON Charles Witton Blackburn SMITH W/50/62

Lancashire Death indexes for the years: 1904
CLARKSON Charles 0 Witton Blackburn W/30/79