Apolgies.... ambiguity!......I'll reorder the sentence:
It was back in the middle of the 19th century that the Swiss researcher Louis Agassiz first determined that there had been an ice age (in recent geological history). People then had been looking for evidence of the Biblical flood but did not suspect an ice age event, so Agassiz' observations were not popular. There is no evidence for a global flood but there is coherent and tangible evidence for a succession of ice age glacial events over the last 2.6 million years.
No earth scientist could survive at his or her job believing the folk tale of Noah's flood to be a true happening.
Why is it so hard for some to distinguish between fact and fiction?