Interesting reading, Charles Darwin's letters. He was both a dandy and a very astute thinker when he put his mind to it.
I find that I enjoyed reading those and will enjoy finding other Darwin letters online - yes I'll now be going to search for them.
For instance, I had a blue-eyed white tom cat - who was deaf. Darwin was very keen of observation to have picked that conection up before Mendel made his far more detailed studies which confirmed this and other genetic rules.
And, you know, history might have been quite different if Darwin hadn't written his book, so it's probably a good thing for us today.