meme at dunadan request

What on earth (or in heaven or anywhere else for that matter) is a meme? Split it and it looks very self-centred ( me me) and I'm bad enough there already! Or is it an acrostic -'make every memory exciting' (that would be fun!), or perhaps, 'most Englishmen marry Engishwomen' -(though I happily married a Scottish girl). However the dunadan in a recent blog challenges(?) me to go to page 123 and perform a task, so for what it is worth, here it is:

St Pancras Station by Simon Bradley

"Communication between storeys was by means of speaking tubes, set likewise alongside the service lifts. All these facilities were grouped vertically, like the service cores of modern steel-or concrete-framed buildings. There was also a sealed shaft for 'dust', which would have included ashes from the hundreds of fires, and even a tube for the stream of outgoing letters: the usual method of public and private communication in the days before telephones, when the penny post within central London would normally achieve delivery later the same day."

Post the same day? Them were the days!