A bequest is a legacy, usually a gift of real estate by will.
Mitochondrial DNA (mtDNA) is the genetic material found in mitochondria. It is passed down from females to both sons and daughters, but sons do not pass down their mother’s mtDNA to their children.
A Blog is an abbreviated version of Weblog, a term used to describe Web sites that maintain an ongoing chronicle of information. There are many blog's for genealogy including the VGS blog and one of the more notable blogs belongs to Dick Eastman. See http://blog.eogn.com
Both Civil Registration and Census Returns run out when you get back to about 1840, and rarely provide information relevant before 1800. At this stage you need to turn to Parish Records: These date back to the mid 1500's. Cromwell, at the Court of Henry VIII, ordered that every wedding, baptism and burial should be recorded.
The 1900 and 1910 censuses lists the number of years of marriage for each married household member.