_et seq_.]

The next step was to count the marriages announced in the "_Pall Mall
Gazette_" for the years 1869-72 and a part of 1873. Of the 18,528
marriages there found, 232 or 1.25 per cent were between persons of
the same surname. Deducting the percentage of chance marriages at
least 1.15 per cent were probably influenced directly or indirectly by
consanguinity.

Mr. Darwin then proceeded by a purely genealogical method. He found
that out of 9,549 marriages recorded in "Burke's _Landed Gentry_," 144
or 1.5 per cent were between persons of the same surname, and exactly
half of these were first cousins. In the "_English and Irish Peerage_"
out of 1,989 marriages, 18 or .91 per cent were same-name first cousin
marriages. He then sent out about 800 circulars to members of the
upper middle class, asking for records of first cousin marriage among
the near relatives of the person addressed, and obtained the following
result:

-----------------------------------------------
Same-name first cousin marriages | 66
Different-name first cousin marriages | 182
Same-name not first cousin marriages | 29
-----------------------------------------------

These cases furnished by correspondents he calculated to be 3.41 per
cent of all marriages in the families to which circulars were sent.

From the data collected from all these sources Mr. Darwin obtains the
following proportion: