The IGI gives one additional child to Jeffery, a Thomas bap. about 9 May 1819, who died 5 days later, 14 May, at Stoke.Mary Anne also died in 1819.I have not determined Amelia's fate.
It would appear that Jeffery's eldest son, Frederick Horswill, is the man of that name who went to Australia (perhaps the one who arrived with wife in 1837, although if so she didn't survive long).Born ca. 1810, he married at Sydney in 1845, Mary Sawyer (or Lawyer as in the Ancestral File), and they had three children, Frederick Jeffrey, Mary Matilda, and David Jesse.He then went to San Francisco, where he was a policeman, and remarried to a Sarah, and later to Coos City, Oregon, where he was a Justice of the Peace and again married (4th?), to Eliza Burt. At least three generations of descent can be traced in California.