Interesting.  Have you looked at Tobias Horton?  He had land around Fleets Bay / Corotoman Creek, not so far from where Henry Johnson seems to have been located.  I have no evidence for this suggestion, other than the fact that he was in the general vicinity. 

Regarding the Robert Newsom who qualified as one of the administrators of Henry Johnson's estate, have you seen the deed in which Henry Johnson witnessed the sale of land to George Chewning?

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1706-1710 Lancaster County Deeds: pg 324-326
THIS INDENTURE made the Eleventh day of Novembr: in the yeare of or: Lod one thousand seaven hundred and nine, BEtweene JOHN PINES and MARTHA his Wife of the County of Lancastr:, Planter, of the one pty., and GEORGE CHEWNING, SENR., of the County aforesaid, Planter, of the other part; Wittness that the said JOHN PYNES and MARTHA his Wife for a valluable consideracon to them in hand paid or secured to be paid, have sould unto GEORGE CHEWNING his Executors and Administrators & assignes one parcell or tract of land lyeing in the County aforesaid and bounded as followeth, (vizt), Begining att a corner marked tree standing by the ISLAND GATE & running downe a line of marked trees to a Marsh called the WHITE MARSH, and soe bounding on the said Marsh to a Creeke called the OLD HOUSE CREEKE, soe running downe the said Creeke to RAFPAHANOCK RIVER side, soe upp the River to ROBERT NEWSOMs CREEKE and from thence to the first station all which tract of land is commonly called by the name of JOYCES NECK, containing in the whole by estimacon Two hundred acres of land wch: pr:misses wth: their appurtenances are parte of a tract of land which was granted by Pattent unto JOHN PYNES, SENR., deceased, by Sr. WILLM. BERKLEY, Knt., Lt. Governor of Virginia hareing date the 14th day of Xber: 1665 as by the said Pattent relacon being thereunto had more plainly will appeare, To have and to hold all and singular the sd. Land and pr:misses unto him the sd. GEORGE CHOWNING his heires & assignes for ever in as large and beneficiall manner as the said JOHN PYNES, his heires or assignes may have or claime to have by virtue of the before recited Pattent or by any other ways and the said JOHN PYNES and MARTHA his Wife doth further covenant and promise for themselves their heires that the aforesaid demised pr:misses is free and cleare from all manner of debts, rights of Dower, incumbrances whatsoever, and that it may be lawfull for ye said GEORGE CHEWNING his heires to hunt hawk fish and fowl on any parte of the whole Island, and allsoe to have use of the whole Island for the range of his or their Stocks eyther of Hoggs or Cattle but not to dispose or allow of the said previledge to any tenant or other p:son whatsoever, and the said JOHN PYNES and MARTHA his Wife doth furthr promise that att the next Court to be held in the County aforesd., that the said JOHN PYNES and MARTHA his Wife will acknowledge this p: sent Bill of Saile for the track of Land to him the said GEORGE CHEWNING, In Wittness whereof the said JOHN PYNES and MARTHA his Wife have hereunto sett their hands and sealer the day and yeare first above written
Signed sealed and delivered in the pr:sents of us
HENRY JOHNSON, JOHN PYNES
ALLEX: MARSHALL, MARTHA PYNES
Febry; 8th 1709/10. JOS: TAYLOE, Clk"
----

This record, and others, suggest that Henry Johnson was probably located near Robert Newsom.  If so, I wonder whether there mightn't have been a relationship (familial or financial) which would explain why Newsom qualified as administrator.  Have you come across any evidence of a Johnson-Newsom relationship?

Another question, a little complicated: is it possible the two Henry Johnsons in Essex County could have been related?  Records cited at http://www.reocities.com/janet_ariciu/Gregory.html make me wonder.

28 Feb 1652/3 r 6 Apr 1653 Lancaster Co: Richard Coleman patent, 320 a. N side Rapp.River near land of Wm.Newsome & land now in poss of Rice Jones; pat issued by Sir Wm.Berkeley. Coleman assigns right to Robt.Mascall wit by Thos.Roots, Rice Jones. Mascall assigns his right to Rice Jones. Wit: Edwin Conway, John Walker. Rice Jones assigns 28 Feb 1652/3 his right in the land to Howell Powell & Geo.Harris, Wit: Edwin Conway, John Walker. 28 Feb 1652-3 Howell Powell ass his right to CHARLES SNEADE, Wit: Geo.Beach.

William Newsome was the father of Robert Newsom (d. 1695) and grandfather of the Robert Newsom who qualified as Henry Johnson's administrator in 1722.  

17 Feb 1700/01 p 10 May 1701 Essex Co VA: RICHARD GRIGORY will, of Farnham Parish in Essex Co VA: to eldest son Richard - land; to dau Eliz'a Grigory land adj that of Robt.Halsey, etc. To son John Grigory 300 acres, being part of 1000 acres formerly patented by Thomas Gaines. To dau Sarah Grigory 700 acres lying upon the head of Matapony River adj land of Capt. James Taylor and Mr. Jonathan Fisher. To "my two sons in Law Thomas and William Borne" each 150 acres at upper end of land given daughter Sarah. Item I give to my son Richard Grigory a Table that is in King and Queen Co and my Caine my Pistolls and a Sword and a paire of Iron Doggs and one Feather bed and furniture. Son Richard to be of age at 18. Item I give to my son John Grigory another Table which is in King and Queene County and one Large Iron Pott which is in King and Queen and one Pott hookes and a Sword and Cubboard and that he be of age at Eighteene. To wife Katherine Grigory balance of personal estate. She sole Extrx. s/ RICHARD GRIGORY. Wit: Anne x Morton, John x Richards, Ja.Clerke.

Robert Halsey, who owned land adj Richard Grigory/Gregory, sold 50 acres to Thomas Johnson, and Thomas Johnson sold 50 acres to Henry Johnson, in 1702.  Presumably this is the Thomas and Henry Johnson who bought land on Dragon Swamp?        

And Richard Gregory's "sons in Law" (stepsons, I guess) Thomas and William Borne might have been related to John Bourne, who stood security for Christian Johnson's administration of the estate of Henry Johnson:

1703. Vol. 29, Essex County (p 6 or Vol. 29, page 29) 10 July 1703,. 20,000 lbs. Tobacco. Christian Johnson as Executrix of Henry Johnson, deceased. Signed Christian Johnson; Edward Price; John Bourne. Recorded 10 July 1703., (From records furnished by Willa M. Moore, Kansas City, Mo. )  (Quoted at http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=GET&db=mrmarsha&id=I25665)

A webpage on the same site (http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=GET&db=mrmarsha&id=I31117) gives a transcription of the will of John Bourne, and shows his wife as Elizabeth Johnson, daughter of Henry Johnson (d. 1702)

James Boughan, who deposed concerning the name of Henry Johnson's wife, signs as security for Katherine Gregory's administration of her late husband's will:

10 May 1701, L 300 Sterl: Katherine Grigory as Extrx of RICHARD GRIGORY. s/Katherine x Gregory, Thomas Edmondson, James Boughan. Wit: Francis Meriwether, Henry Goare. 

Richard Gregory's wife Katherine married Thomas Snead by 10 Nov 1702:

10 Nov 1702 Ess.Co: RICHARD GREGORY Inv of Est taken by Court order 10 Nov 1702 covering 3 pages, total value L 85. 9.8. s/Wm.Johnson, Leonard Chamberlaine, John `Games'. Sworn before Robt.Coleman 29 Dec 1802. Note of 2 mares sold for 1000 lb tobo by THOS.SNEAD. Presented by THOMAS SNEAD & KATHERINE his wife 10 Jul 1703 & recorded. (VCA II, p 93)

Katherine Gregory's husband Thomas Snead was the son of Charles Snead who in 1653 had acquired land on the N. side of the Rappahannock"near the land of William Newsom".  Katherine seems to have been born Katherine Chowning/Chewning, sister of Thomas Chowning (d. 1688):

Abstracts of Lancaster County, Virginia Wills 1653-1800; {Ida J. Lee}
CHOWNING, Thomas. Will. 14 Jany. 1678. Rec. 16 Jan. 1688.
Wife Ann (also Extrx) Sister, Katherine Gregory; god-dau. Margaret Merriman; Cozen Thomas Chowning, Cozen Robert Chowning, Cozen Katherine Chowning. Wits. David Fox and Richard Flint. W.B. 5, p. 128

1687-1691 Lancaster County Order Book 3: pg 98
Lancaster county Court 9th of January 1688/9
- A P:bate of the last Will and Testamt. of Mr. THOMAS CROWNING, (deced), is granted unto MRS. ANN CHOWNING, his Widdow and Relicte, according to the tenor of the said Will. EDWARD CARTER, ROBERT NEASUM, Mr, RICHARD MERRIMAN and Mr. JOHN SUMNER are ordered to appraise the saide Estate on the 18th Instant and was sworne in Court. An Inventory to bee exhibited to the next Court
===
1687-1691 Lancaster County Order Book 3: pg 99
Lancaster county Court 13th of February 1688/9
- MRS. ANN CHOWNING, Executrix of the last Will and Testamt. of Mr. THOMAS CHOWNING, (deced), appeareing greatest Creditor to the Estate of WILLIAM CLEMENS, (deced), Commission of Administracon according to Acte is therefore granted unto the saide CHOWNING, she giveing security according to Acte. EDWARD CARTER, ROBERT NEASUM, JOHN SUMNER and JOHN HARRIS are ordered to appraize the saide Estate and were sworne by the Court, An Inventory thereof to bee exhibited to the next Court. WM. MERRIMAN, security

Robert "Neasum" being Robert Newsom, father of the Robert Newsom who qualified as an administrator of the estate of Henry Johnson in Lancaster Co in 1722.

All of which leads me to wonder whether the two Henry Johnsons in Essex County might have been from the same Johnson family, though I can't at present suggest in what way they might have been related.      

Most of the records I've cited appear at http://www.reocities.com/janet_ariciu/Gregory.html.  None of it is my research. 
     

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