"Man stands with bowed head in the presence of nature's visible grandeurs, such as towering mountains, precipices, or icebergs, forests of immense trees, grand rivers, or waterfalls. He realizes the force of waves that can sweep away light-houses or toss an ocean steamer about like a cork. In a vessel floating on the Gulf Stream one sees nothing of the current and knows nothing but what experience tells him; but to be anchored in its depths far out of the sight of land, and to see the mighty torrent rushing past at a speed of miles per hour, day after day and day after day, one begins to think that all the wonders of the earth combined can not equal this one river in the ocean. "

--Pillsbury

Not the passage I recalled, but a good idea of what I was talking about.
It probably was from one of the other ships, like the Blake. Until modern electronic nav systems were first introduced in the 40s, deep anchoring was the only way to get an accurate current reading at a particular spot and time.