More units of measure: acres

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Mark Brader - 27 Dec 2008 20:45 GMT

As everyone knows,

1 yard = 3 feet
1 rod[A] = 5.5 yards = 16.5 feet
1 chain[B,C] = 4 rods = 22 yards = 66 feet
1 furlong = 10 chains = 40 rods = 220 yards = 660 feet
1 mile = 8 furlongs = 80 chains = 320 rods = 1760 yards = 5280 feet

1 acre = 1/640 mile² = 1/10 furlong² = 10 chain² = 4840 yd² = 43560 ft²

[A] Also called a pole or perch
[B] Also equal to 100 links.
[C] This is also called Gunter's chain. Another unit called
a chain is equal to 100 feet, but that's not important now.

So a field that is 1 chain wide by 1 furlong long has an area of
1 acre. Remembering that the "fur" in "furlong" is a furrow, it
should be clear that this is the origin of this unit.

However, I recently came across a couple of older passages (details
below), where "acre" seemed to be being used as a unit of length.
I looked at Russ Rowlett's web site and there was nothing about it
there. I then looked at the OED, where the word "acre" was included
in the very first fascicle to be published:

# 3. As a lineal measure: an "acre length", 40 poles or a furlong
# (i.e. furrow-length); an "acre breadth", 4 poles or 22 yards.
# Obs. or dial.

In other words, by this usage, which was already obsolete (or dialect)
in 1884 when this entry was written, an acre (of) breadth is a chain,
and an acre (of) length is a furlong. The last cite in the OED is
from 1809.

But that was not consistent with the way I had just seen them used.
While the exact meaning is unclear (and I'll go into the possibilities
in detail below), it is clear that the unit in question is somewhere
around 3 or 4 chains.

My source was letters quoted in the 3-volume work "Men and Meridians:
The History of Surveying and Mapping in Canada", written by Don
W. Thompson and published in 1966-69 by the Canadian government's
Department of Energy, Mines and Resources.

The first passage, on page 199, is from a letter written by Miles
Macdonell, first governor of the Red River colony, to Lord Selkirk,
who sponsored the colony, apparently on 1813-07-17 (in one place
the book gives the date as 1883, but this makes no sense and must
be a typo; the book contains an annoyingly large number of things
that "must be typos"). Ellipses and square brackets as in the book.

| ...I have since laid out lots of 100 acres, of 4 acres front
| on the river, according to the annexed rough sketch...
| The farms of Lower Canada are only 3 acres front, and the
| first settlers in Upper Canada had only the same, but they
| found it afterwards too narrow, which induced me to add one
| acre additional to the breadth of our lots here. This [is]
| sufficient for any farmer...

(The Red River colony, Lower Canada, and Upper Canada correspond
respectively to the first-colonized parts of today's Manitoba,
Quebec, and Ontario.)

Okay, what does that mean? When these parts of Canada were surveyed
into lots for settlers, they were elongated rectangular lots (rather
than the square lots used in western Canada and much of the US)
-- but not as elongated as 4 x 250 chains, which is what it would
mean if "4 acres front" was the "4 acres breadth" of the OED entry.

Could the letter be using the concept that an "acre" in this context
represents a rectangle of a specific shape as well as a specific
size? I have never heard of such a thing.

The corresponding French unit for area at this time was the arpent,
and according to context this name was also used for a linear unit.
Linearly it was equal to 191.838 feet or 2.90664 chains; as an area
unit it was the square of this, or 0.84485 acre. Is it possible
that this in Canada this notion was copied back into British units
and an "acre" of linear measure meant the *side of a square* whose
area was 1 acre? This seems even less likely to me, as it would not
fit conveniently with *any* other units -- this "acre" would be equal
to sqrt(10) = 3.162278 chains or 208.7103 feet or 208 feet 8.5+ inches.

Unfortunately, the "annexed rough sketch" is not reproduced in the
book. Immediately after quoting the letter, the book goes on:

| Lord Selkirk advocated a more compact type of settlement
| but this was never established, the river-lot system
| prevailing. Thus more than a thousand miles from the
| St. Lawrence Basin, history repeated itself. Talon and
| Colbert had suffered a similar reverse in New France of
| the 17th century. By 1870 river lots extended for more
| than 40 miles along the Red, and along the Assiniboine
| as far as Portage la Prairie. Most of the lots were laid
| out with a 12-chain river frontage but there were later
| variations all the way from 1 chain to a half-mile in width.

The business about "river lots" and the St. Lawrence Basin is that
when the French owned the colony (under the name Nouvelle France
or New France), they generally surveyed the land there along each
river into long narrow lots with one end on the river, so that
everyone would be able to use it.

Elsewhere the book says in reference to New France that "the average
farm had a frontage of three or more arpents and by [sic] a depth of
thirty or more arpents, but here again there were variations".
Could Macdonnell be thinking of an arpent as a French acre and using
"3 acres front" loosely to mean 3 arpents? This seems unlikely in a
context calling for precision; I'm sure he wouldn't be using French
units for new surveying, as with the "4 acres front".

Then on page 221 of the book is another letter with a similar
usage, but with interesting detail in addition. This one is dated
1783-09-11 and was written by Sir Frederick Haldimand, Governor of
Quebec, to his deputy surveyor general, John Collins. ("Quebec" at
that time was the same area that in 1813 was Upper and Lower Canada.)

| 4. The method of laying out townships of six miles square
| I consider as the best to be followed, as the people to
| be settled there are most used to it, and will best answer
| the proportion of lands I propose to grant to each family,
| viz: 120 acres, of which six are to be in front, which will
| make 19 chains in front and 63 chains 25 links in depth, so
| that every township will have 25 lots in front and 4 chains
| 75 links will remain for roads, with 7 concessions in depth.
| Fifty-eight links will remain for a road, by which distribution
| each township will contain 175 lots of 120 acres.

(A "concession" is a row of adjacent elongated rectangular lots with
their short ends along a common pair of parallel lines.)

Note the "of which six". This really makes it sound as though he's
thinking of an acre as having a specific shape, rather than referring
to acres of area and then, in the same sentence, acres of length.
But he might still really be intending the latter.

It would help if the numbers fitted together, but I can't make them
do so. Maybe some of them are supposed to be approximate, but he
doesn't hint as to which ones. He's talking about taking a 6-mile
square township and dividing it into a 7x25 grid of rectangular lots
plus road allowances. If each lot is exactly 19 x 63.25 chains,
that makes it really 120.175 acres. An exact 120 acres with 19
chains front would be only 63.16 chains long.

The other thing that isn't clear is the layout of those roads that
there are allowances for. As there is no diagram of this layout,
all I have to go by is Southern Ontario, which also used townships
and concessions but not so regularly shaped. One common pattern
had lots of 20 x 100 chains (thus 200 acres) with roads every 100 chains,
forming a square grid with 5 lots in each square. But that pattern
doesn't exactly translate to lots of 19 x 63.25 chains.

Haldimand's mention of two different numbers, 4.75 and 0.58 chains,
for road allowances suggest to me that there was allowance for a grid
of roads, north-south and east-west, but with different spacing.
But 19 x 25 is 475 chains, and 63.25 x 7 is 442.75; the difference
between these numbers and 6 miles (480 chains) is respectively 5.00 and
37.25 chains, nothing like the numbers actually mentioned.

Anyway, if we assume that 19 chains is exact, and if "acre in the front"
is meant as a linear unit, then that unit must equal 19/6 chains or
exactly 209 feet. This is quite close to the sqrt(10) value given above.

The result is that I'm still puzzled, and I wonder if Evan or anyone
can turn up another source that might clarify what exactly these guys
were talking about.

Signature

Mark Brader | "Opening a monitor case is not for the inexperienced
Toronto | or the faint of heart, unless you need
msb@vex.net | defibrillation." -- Kevin D. Swan

My text in this article is in the public domain.

Discussion Groups / English Usage / January 2009

More units of measure: acres