Fizeau 1851: does the medium drag the light?
Fact (secondary sources: Wikipedia, Grokipedia): Fizeau measured light in flowing water in 1851 and found a real but smaller-than-full dragging effect, matching Fresnel's partial-drag coefficient f = 1 - 1/n^2 (about 0.44 for water).
Disputed: sources date Fresnel's proposal differently (1818 vs 1846). Primary texts unread.
Later: Einstein's 1905 special relativity re-explained the result without any ether.
Aetherist reading (interpretation): a medium that only partly carries what passes through it. Belief, like the ether, drags us partially: never zero, never total.
Open question: Lorentz-FitzGerald contraction was not covered by these pages; needs its own chapter.