“I am currently dealing with a 1972 lease which describes the property as ‘ALL THAT piece of land containing 16 poles or thereabouts and situate at…’
“I am old enough to remember the ‘rod, pole or perch’ form of measurement, but cannot recall the area of same, also that the chain was used in the measurement of length.
“An article on these and other forms of ancient measurement, such as the bushel, would be of interest.”
Surveyors do need to be aware of the old traditional square measurements, as these will occasionally appear on old deed plans, such as the one illustrated opposite. This is particularly true in rural areas where parcels of land are still identified in terms of “acres, roods and perches”.
History
In the modern, scientific world, we have come to accept clearly defined standards of measurement, so that, whether adopting metric or imperial units of length or area, the surveyor can be clear and precise about what is meant by that particular unit. Such precision, however, was not always possible and in ancient societies neither the need nor the technology existed to encourage or enable the development of accurate and consistent systems of measurement. Different societies tended to develop their own distinct systems. However, with increased trade, expansion and conquest, the influence of Greek, Roman, Egyptian, Chinese and Babylonian cultures tended to spread. Even so, the need for precise measurement arose only with the development of scientific activities such as astronomy and navigation during the middle ages and then, later, with the industrial revolution of the 18th and 19th centuries.
Body measurements formed the earliest convenient bases for linear measurements. The Egyptian cubit is thought to have been devised around 3000 BC and was defined as the length of the arm from the elbow to the tips of the outstretched fingers. This was made up of a number of digits based on the breadth of the finger. Four digits equalled a palm and five a hand. There were 28 digits in the cubit. The Greeks adopted a system where 16 fingers (each with a width of 19.3mm) was equal to one foot, which was, therefore equivalent to about about 30cm. The Romans adopted the Greek system but subdivided the foot into 12 unciae (inches). The inch is also thought to be derived from the Anglo Saxon “ynce” which means a 12th part. A double step or a pace was equal to 5ft and a 1,000 paces made up a Roman mile (mille passus), which at 1,667 yds, therefore, was not so dissimilar to the statute mile of today. For many years the actual length of the mile remained subject to local variations, the Irish mile, for example, at 2,240 yds remained in existence well into this century. Not surprisingly, it was the Roman system which had the greatest impact in Europe and Britain.
In medieval times, abuse of weights and measures was widespread, particularly those used for commodities such as grain and wine. The need for reliable and accurate systems was recognised by a clause in the Magna Carta and, not long after 1215, a royal ordnance, entitled “Assize of Weights and Measures”, defined a list of standard units. In linear measure the ordnance identified the standard yard, made up to 3ft each of 12ins, and the rod as 5 1/2yds or 16.5ft.
The rod was an old English linear measure which was also known as a perch or a pole. Rod is thought to be descended from the Dutch “rood”, which, in turn, can be traced back to the German “rute”, which means rod (it seems also to be defined as a particular part of the male anatomy). The Dutch rood was in fact a square measure being an area of land of 1 rod in width and 40 rods in length, and which was equal to a quarter of an English acre. As with the concept of the mile, the early rood was a variable quantity, the term being loosely applied locally to any small area of land. The rood as a precise quarter acre however, still exists today.
The acre was estimated as the amount of land that could be ploughed by a horse in a day. This was taken to be 40 rods, poles or perches in length and 4 rods in breadth. The length of this acre was a furlong “furrow long”. The width of the furlong was divided into 72 furrows, each 11 inches in width. So the acre was equal to 160 sq rods. Over time the acre came to mean an area of any shape which amounted to 4840 sq yds.
A significant development in linear measurement occurred in the 17th century with the introduction of the chain. The mathematician, Edmund Gunter took the acre’s width, 22 yds, and divided it into 100 links to be used as a measuring device. There are 80 chains to the mile and this is equal to 320 rods, poles or perches. An English acre is 10 sq chains which is 4 square roods.
The bushel is a unit of capacity which appears on both sides of the Atlantic. In the UK it was used as a measure of both liquid and dry quantities, in America it is a dry measure only. In 1701, the corn bushel, a unit of dry measure was defined as “any round measure with a plain and even bottom, being 18 1/2ins wide throughout and 8ins deep”. Since 1824 in England it has been defined as 8 imperial gallons or 4 pecks.
The metric system
It can be seen that the British imperial system of weights and measures, with its legacy of sometimes confusing and even variable units, grew more or less haphazardly out of custom. The metric system is a planned system with a more rational foundation and is more widespread than the imperial system whose last outposts seem to be confined to the UK and former commonwealth countries and the United States.
A 1963 Act of Parliament redefined English weights and measures in terms of the metric system, with a national changeover to the metric system to begin two years later.
The metric system itself was established following the French Revolution. The need for a consistent standard of measurement was recognised and, sensibly, one of the main criteria for such a system was that it should be decimal-based. Another consideration was the need for a physical standard of reference. It was decided that the basic unit of length, the metre, would correspond to a 10,000,000th of the distance of the meridian passing through Paris from the North Pole to the equator. This was established by physical survey and from astronomical data.
The metre became the standard linear unit with fractions and multiples being identified by Greek prefixes. The unit of area was the are, a 10m x 10m square, although in practice the hectare – 100 ares – has become the principle unit of area within the modern metric system.
Mass and cubic capacity were also based on the metre: the gram being the mass of a cubic centimetre of pure water and the litre being the volume of a cube each side of which has a length of one decimetre (10cm). With further scientific development in the 20th century, the need for greater accuracy made it necessary to adopt more accurate standards. The SI (Systeme International) was determined in Paris in 1960 at the 11th General Conference on Weights and Measures, which adopted and defined base units for length, mass, time, electric current, thermodynamic temperature and light intensity. The metre was defined as “1,650,763.73 wavelengths in vacuum of the orange red line of the spectrum of krypton-86”. A little more accurate than the the figure derived from the original Delambre-Mechain survey of the Paris meridian!
Surveyors and the metric system
It is perhaps coincidental that topic of ancient measurement is raised at a time when the issue of metric and imperial is again being aired in the columns of the Estates Gazette.
The general view of the surveying and estate agency professions seems to be to favour the continued use of imperial units of square and linear measure, on the grounds that these are what the client wants and understands. This seems to be faintly insulting to the intelligence of the average client. Having been metric since the 1960s, “it is high time that the outdated surveying arm of the construction industry came into line with architects, engineers, quantity surveyors and contractors[1] “. But the most persuasive ]argument for the use of metric units, if further is needed, is surely the comparative ease with which area calculations can be undertaken. If imperial linear measurement is used on say a large office block valued using net internal area, every single linear measurement needs first to be converted to its decimal equivalent before the area can be calculated.
As the chairman of the RICS/ISVA Working Party, responsible for the Code of Measuring Practice, points out: “Metric units will become the principal unit of measurement for almost all areas” with effect from January 1 1995, although after that date, there will be a phasing-out period during which “imperial measurements may be used as a supplementary indication, provided that the metric unit is predominant[2] “.
In my student days, when polytechnics were just polytechnics, there was no question of using anything other than metric. As one recent Estates Gazette correspondent put it: “Buildings are actually built with metric bits[3] ” and have been so since the late 1960s. However, I remember the puzzled look on my supervisor’s face as I read off from the tape in metric on my first survey. I recognised then that the average practitioner had a different view of the world and so learnt how to convert from metric to imperial and vice versa.
It seems ironic that the move to metric usage has lost much of the impetus it had in the late 1960s and that certain elements of the surveying profession would appear to be as much to blame as anyone. It is surely an evasion to blame the client, for these are the same clients who have been, despite the odd reference to shillings and “10-bob bits”, coping quite admirably with decimal coinage since 1971.
Finally, as a sop to the committed Luddites, but also to enable the enlightened to communicate with imperial dinosaurs – a conversion table:
References
[1] Estates Gazette, “Correspondence”, p47, November 21 1992.
[2] Estates Gazette, “Correspondence”, p59, September 19 1992.
[3] Estates Gazette, “Correspondence”, p39, January 16 1993.