Archive for July, 2011


The first entry in Thoreau’s “Field Notes of Surveys” dated November 1849 contains comments describing a survey of Isaac Watt’s Woodlot. 

 “Outlines measured with accuracy, corners being one tenth of an angle.”

Copy from CFPL microfilm:

copy of the survey may be viewed at http://www.concordlibrary.org/scollect/Thoreau_surveys/135.htm

The survey image includes a worksheet on which Thoreau listed and then incorrectly computed the total area for 14 odd shaped lots as = 907 square rods (907 /160=5.66 acres).

By my calculation the correct sum of the data for the 14 odd shaped lots listed is 947 square rods=5.91 acres, a difference of 40 square rods or a 0.25-acre under count by Thoreau.

In addition, Thoreau identified 38 uniform quarter acre lots/4=9.50 acres.

Grand total area = 9.50 uniform quarter acre lots plus either 5.66 acres or 5.91 acres odd shaped lots = 15.56 or 15.41 acres, a difference of 0.25 acre.

At the end of his “Field Notes of Surveys” for Isaac Watt’s Woodlot Thoreau said:  “Surveyed 52 lots of a quarter of an acre and some cases more.”

(All but one of the odd shaped lots was more than a quarter acre.).

 In summary, Thoreau undercounted the total acreage of Isaac Watt’s Woodlot by 0.25 acres on his worksheet, but his survey map is correct.

 Thoreau only said he surveyed 52 lots which is true and the average lot size for the combined quarter acre 38 uniform shaped lots and 14 odd shaped lots equals slightly more than 15 acres, just as Thoreau described  “52 lots of a quarter of an acre and some cases more”. 

So although Thoreau’s table of odd shaped lots appears to contain an undercount error of 40 rods or 0.25 acre the error as a percent of the total area is small (0.25/15= 1.7%) and the map contains other known inaccuracies such as Thoreau notes that “Greatest error in IK & KL” which appears to be a zone edge approximation along its Virginia Road boundary across the road from Thoreau’s birthplace and current Headquarters of the Thoreau Society.

Nevertheless, Thoreau had recorded a survey of “52 lots of a quarter of an acre and some cases more” for Isaac Watt’s Woodlot during November 1849. 

 “V  Plan in pencil”

For more details and help locating each of the 14 odd shaped lots and 38 uniform shaped quarter acre lots covering 15.56 acres of Isaac Watt’s Woodlot see my discussion at: https://aschmidt01742.wordpress.com/2010/03/07/thoreaus-1849-survey-of-isaac-watts-woodlot/

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“There are three stages of scientific discovery: first people deny it is true; then they deny it is important; finally they credit the wrong person.”
— Alexander Von Humboldt


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