In general throughout the Glens, whatever grazing there is on the mountain is divided between the various holdings of the adjacent lowlands. The division is made by each denomination possessing so many “sums”, the larger holdings having more sums and the smaller holdings fewer. The value of the sum will vary from district to district according to custom and the relative richness of the mountain grazing. Each sum represents the right to graze so many animals. The following unsigned memorandum gives an interesting example of how the system works.
"We the undersigned persons do agree to sum and think our Mountain in this way. First Garfore (townland of Gartford); Robert Craig one third, ten sums; Charles O’Boyle one third, ten sums; John McCavock one sixth, five sums; Charles McAulley one sixth, five sums, Gortgarney John and Robert McNeill one third ten sums Neal McCambridge one third ten sums William McKillop one twelfth two sums and one half John McKillop one twelfth two sums and one half Hugh McKillop one sixth five sums Northunchanagh Daniel McNeill and Margaret McNeill one eighth three sums and three fourths of a sum John McNeill one eighth three sums and three fourths of a sum Robert McNeill one eighth three sums and three fourths of a sum Hugh McNeill and Neal McCambridge one eighth three sums and three fourths of a sum Jasper McKillop one eighth three sums and three fourths of a sum Elizabeth McKillop one eighth three sums and three fourths of a sum Hugh Ford and John Gill one eighth three sums and three fourths of a sum Southunchanagh William Gipson one half fifteen sums John McGill one half fifteen sums and further Take Notice that each town is to have six horses fole [sic] or no fole for six sums Each man to have a horse or horses according to his holding Every horse fole or no fole above six shall or may be counted one sum and one half Every heifer three years old and upwards one sum Every two year old and one year old mutton one sum three of one year old make one sum Six ewes and lambs one sum the lamb not as a sheep to (till) it be one year old Eight Gel sheep for one sum.” May 18th, 1825.(The original has no punctuation whatsoever. The four townlands mentioned lie at the mouth of Glencloy.)
From The Glynns, Volume 2, 1974.