Love the premise and I see several years are posted. I like your philosophy of science section especially, because while most would neglect that area, it's probably got good predictive/foreshadowing juice in general (although not necessarily for any given year).

Skimming https://en.wikipedia.org/wiki/1875_in_science the twin studies and behavioural genetics is interesting. The challenger-deep thing too since it's earlier than I would have guessed, but IMHO it would be more exciting/appropriate to categorize as "exploration" than science. Did they publish a "paper" about stuff like that back then, or just tell the royal society, tell the newspapers and call it good?

A pointless but fun question to think about is, how to decide the most important thing that happened in a given year? Sometimes a discovery, sometimes an idea, sometimes a project, election, or war. But for a slow year.. maybe it's just that someone who will have that idea or start that project later was born.

I find the naturalism vs spiritualism debate to be one of the most compelling parts of what's going on in the late nineteenth century and plan to continue covering it in future installments.

It's always an interesting exercise choosing which books or articles to write about. There's a balancing act between what I want to read, what I think is important or representative, and what do I know enough about to have anything to add.