T 6 N, R 5 E, Fifth Principal Meridian | Double Corners
I need to revise what I said above. The south half of Sec. 4 and Secs. 9, 16, 21, 28, 29, 32 and 33 were not lotted on the 1847 plat. Instead they were classified as being a fractional half section and fractional sections respectively. Also, there are no field notes for the 1847 plat. The GLO redrafted the 1824 plat in 1847. I didn't notice in my first post that the dimensions are identical on the two plats.
The 1847 plat states that the south township line was surveyed by two different deputy surveyors; secs. 31 through 33 in 1816 and 34 through 36 in 1823. From the distances of the north lines of Secs 31, 32 and 33 it appears that the 1816 deputy's chain was long by a little over 3 links. You can see that by looking at the fractional section subdivisions in Secs. 32 and 33 where the south lines are held to be 80.00 chains and the north lines are 82.03 and 82.69 chains as returned in the 1824 subdivision field notes (also, the north line of Sec. 31 is 82.86 chains). The 1824 field notes do not indicate that the deputy retraced the south township line.
The 1847 lotting of Secs. 1 through 5 held the southern two tiers of lots at 40 acres to be consistent with the 80 acre lots on the 1824 plat. Oddly the next tier (lots 2 and 3 on the 1847 plat) were not held at 40 acres, but rather the east-west line between lots 2 & 3 and lots 1 was established at 60 chains north of the east-west centerlines of the sections. For Sec. 6, there are 3 tiers of 4o acre lots in the eastern half (lots 2 through 7) since the east/west dimensions are all 20 ch.
So Dan it looks like the GLO draughtsman intended for there to be two sets of double corners on the north/south centerline of Sec. 4 and similar two sets of corners between Secs. 3 and 4 and Secs. 4 and 5. An interesting way that the GLO dealt with a situation 23 years later where the GLO reclassified several sections as being fractional that were reported as regular on the 1824 plat.
And yes, you are correct about military warrants being issued in this area. The GLO Records web site only lists five patents for the township. One is a military warrant issued in 1851 for a corporal in the first Regiment Alabama Volunteers Florida War. The 40 acres was described in the patent as "the North West fractional quarter of the South East fractional quarter of Section Nine....containing 41 acres and 42 hundredths of an acre." Adjacent to this is an 1850 cash entry patent described as "the North East fractional quarter of the South East fractional quarter of fractional Section Nine....containing 41 acres and 42 hundredths of an acre."
A bit speculative on my part, but the CFedS training describes a general rule that GLO draughtsmen supposedly followed regarding lotting. They were supposed to keep the number of lots to a minimum (i.e. keep as many aliquot parts as possible). Perhaps this example is an earlier analogy to that general rule whereby the daughtsman created lots that were 40 acres whenever possible, which just happens to be the smallest legal subdivision.
Of course, that leaves the question of why lots 2 and 3 in Secs. 1 through 5 weren't 40 acres and the excess thrown into the 10 lots numbered as 1. They purposely held the dimension from the east-west centerline of the section to the south line of the lot 1s at 60.00 chains with the resultant cost of having double corners.
I din't have much of an answer for why this was done this way, but except for where there are math mistakes, how to protect the plat on the ground isn't too difficult to figure out. Of course depending on the ownership and what happened in the 172 years since this plat is approved that might not be the way way to go about this.
Something is wrong with the section line between secs. 3 and 4 though...
I'm not sure if this has anything to do with the question, but in Illinois, my area was surveyed in about 1817, but I think this holds true for most of the state, there were corrections at every township line. I'm not sure how far west you go before they only corrected every 4 townships.