The cost per page is calculated based on the cost per ink cartridge and the average number of pages per cartridge, based on the 20% coverage model.
It is named after John Langdon Down, the British doctor who fully described the syndrome in 1866. Some aspects of the condition were described earlier by Jean-Ãtienne Dominique Esquirol in 1838 and Ãdouard SÃ©guin in 1844. In 1957, the genetic cause of Down syndrome, an extra copy of chromosome 21, was discovered.
John Harrison. For other people named John Harrison, see John Harrison (disambiguation). John Harrison (3 April [O.S. 24 March] 1693 â 24 March 1776) was a self-educated English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of calculating longitude while at sea.