1a.  Marriage Index:  Maryland, 1655-1850.  Liahona Research, Orem, UT (Broderbund CD-224):

Sly, Jacob

Lakin, Emaline

26 Jul 1828

Frederick Co.

1b.  Anon.  1966.  Marriage Index:  Ohio, 1789-1850.  Liahona Research, Orem, UT (Broderbund CD-400):

Walcut, Harrison	Slyh, Serena Ann	5 Apr 1848	Franklin Co.
Walcutt, Harrison	Slyle, Rebecca Ruth	23 Oct 1856	Franklin Co.

2.  Census Index:  U.S. Selected Counties, 1830 (Broderbund CD-315):  can't find, but Jacob, his wife, and two youngest children appear to be living with Jacob's widowed father, Mathias SLYH, in Franklin Co., OH. 

3.  1840 Census Index and Digital Images (online at Ancestry.com; Image #9 of 12 — indexed as "Jacob Hugh"; extracted by Diana Gale Matthiesen):

1840

OH

Franklin Co.

Clinton Twp.

pp. 189B-190A

Jacob Sleyh

120 000 100 - 201 001 000 100

0100000

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	4 or under	1835-1840
2 males	5-9	1830-1835	= Henry (b. 1834) = Jacob (b. 1831) = Daniel (b. 1830)
1 male	40-49	1790-1800	= Jacob (b. 1798)
2 females	4 or under	1835-1840	= Mary (b. 1838) = Rebecca (b. 1836)
1 female	10-14	1825-1830	= Serena (b. 1829)
1 female	30-39	1800-1810	= Emeline (b. 1801)
1 female	70-79	1760-1770	= Jacob's mother?
1	person engaged in agriculture

Either Henry is in the wrong age-class or we have his birthyear wrong.  Listed six lines from W. LAKIN, who is two lines from Emeline's father, Daniel LAKIN.

4.  1850 Census Index/Images (online at Ancestry.com; Image #2 of 30):  Dist. 38, Clinton Twp., Franklin Co., OH, p. 62B, 12/13, enumerated 12 Aug 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Jacob Sly	50	M		Farmer	15,000	Va
Emeline	49	F				Md
David	20	M		Farmer		O
Edward	19	M		"		"
Henry	16	M		"		"
Rebecca	13	F				"
Mary	13	F				"
John	5	M				"
Jacob Siller	38	M		Laborer		"
Elisha Hilbert	22	M				"
Julia A Walcut	1	F				"

5.  1860 Census Images (online at Ancestry.com; Image #3 of 36):  North Columbus P.O., Clinton Twp., Franklin Co., OH, p. 132B, PN 264, 1539/1639, enumerated 13 Jun 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Jacob E Slyh	61	M		Farmer	72,500	1,500	Va
Emaline   "	58	F					Md
John W    "	16	M					Ohio
Sarena A Walcut	11	F					Ohio
Charles Nult	22	M		Farm Laborer			Ohio

Which is correct, Julia or Serena?  Living next door to their son, Henry T. SLYH.  Also in Clinton Township is their son, Jacob Edward SLYH. 

6.  1870 Census Images (online at Ancestry.com; Image #7 of 47):  Dublin P.O., Clinton Twp., Franklin Co., OH, p. 38A, PN 7, 48/48, enumerated 11 Aug 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Slyh Jacob	71	M	W	Farmer	118,600	50,000	Virginia
____ Emaline	69	F	W	Keeping House			Maryland
Darson? Lawerence?	21	M	W	Farm Laborer			Hesse Cassel

Living next door to son, John W. SLYH, who is living next door to son, Henry T. SLYH. 

7.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).