Lynda/Stan In the early part of the 19th century the size of an acre differed across the country. What tended to be common I think was that an acre was 10 sq. chains. So the question then is how big was a chain? Many people will know cos' it used to be included in the tables on the back of our sum books at school that a chain - the length of a cricket pitch - is 22 yds. 22 X 22 is 484. A Sq Chain is therefore 484 sq yards and an acre which is 10 sq chains is 4840 sq yds - which might be remembered. So where is all this leading? In the early 19th century, a Cheshire Chain was not 22 yds but 32 yards. A square Cheshire chain was 1024 sq yds. A Cheshire Acre was 10 sq (CHESHIRE) chains - equal to 10,240 sq yds i.e twice and a bit as big as a standard acre :-) I just wondered if your grandfather indicated how big a Durham chain was. I know that Cheshire was not the only odd one out. So was Lancashire. Stan How do you measure the area of a triangle????? To calculate it, multiply half the base times the height. But would they have to measure the height - at right angles of course? How accurate would farmers be? How accurate would be those who calculated the areas of fields for the Apportionments be? I was interested in Lynda's copy books because it might provide the practical method at that time. I have been involved for a number of years as an amateur archaeologist in suveying and laying out sites ie practical mensuration. I'm sorry list if I've gone on a bit about a non family history matter Neil Beattie