Mrs. Loudon’s striking examples are surprising because familiar bodies of water behave in counterintuitive ways: tides do not repeat at the same hour, currents can move independently of wind, seawater can be warmer than the air above it, fresh water can rise through salt water, and lakes can vanish, boil, or lie far below sea level. The following summary preserves her nineteenth-century descriptions and figures as presented, without treating them as a modern scientific account.
The practical surprise is that the tide does not complete its cycle according to the ordinary solar day. Mrs. Loudon describes the lunar day, the period governing the tide’s flux and ebb, as 12 hours and 48 minutes. Consequently, the tide occurs 48 minutes later each day, rather than returning at the same clock time. This daily shift is why sailors need tide tables to predict when the tide will serve, or become favorable for navigation. [1][2]
Mrs. Loudon presents ocean currents as movements that continue independently of the wind, making the sea capable of carrying a vessel even when there is no wind for its sails. She gives the Gulf Stream a speed of 5 nautical miles per hour and identifies it by several visible or sensory signs: unusually warm water, an indigo-blue color, floating seaweed, and warm air around it. [4][5]
The most dramatic calculation concerns the Gulf Stream’s circulation. In Humboldt’s calculation, a single drop of water would take 2 years and 10 months to return to its starting point. Mrs. Loudon translates the current’s power into practical sailing possibilities: a boat without wind or propulsion could, in her account, travel from the Canaries to Caracas in 13 months, circle the Gulf of Mexico in 10 months, and pass from Florida to Newfoundland in 40 to 50 days. [6][7]
The surprise is therefore not merely that the Gulf Stream is warm or fast. It is that a current can function like a vast, slow-moving conveyor, carrying water and potentially vessels across enormous distances while appearing to defy the immediate conditions of wind and sail.
Mrs. Loudon reports that between 27° north and 27° south latitude, sea temperature remains entirely independent of atmospheric changes. She also states that solar rays do not penetrate deeper than 45 fathoms, yet the temperature at the sea’s surface remains 3 to 5 degrees warmer than the air above it. [8][9]
The counterintuitive detail is the contrast between limited solar penetration and persistent surface warmth: although sunlight is described as reaching only a relatively shallow depth, the sea’s surface can still be warmer than the atmosphere immediately over it. In Loudon’s presentation, the ocean is not simply a passive reflector of daily weather but a body with its own temperature behavior.
Another of Mrs. Loudon’s surprises is that fresh-water springs can issue directly from the ocean. She says that in places such as the Persian Gulf and the south coast of Cuba, fresh water rises through the surrounding salt water and remains completely unaffected by it. [10]
The practical and visual oddity is that the boundary between fresh and salt water can persist at the very place where one would expect immediate mixing. A person at sea might therefore encounter drinkable fresh water emerging from the sea itself, according to the examples she gives.
Mrs. Loudon describes the Black Sea as unusually low in salt, sufficiently so that carp and other fresh-water fish can live in it. At the same time, she portrays it as a violently stormy body of water, with tremendous, boisterous tempests and a whirling motion attributed to its being enclosed by land on three sides. She further states that it contains no islands except one in the Bosphorus. [11][12]
Its surprising character lies in the combination of apparently gentle and violent properties: water fresh enough for fresh-water fish, yet a sea capable of immense storms and swirling motion. Its near-enclosure by land is presented as part of the explanation for this distinctive behavior.
Loudon emphasizes that lakes do not always conform to the expected pattern of receiving water through an inlet and losing it through an outlet. Some have neither inlets nor outlets; others receive streams but have no visible outlet while lying many feet below sea level, as with the Dead Sea and Caspian Sea. [13]
These examples overturn the ordinary image of a lake as a stable, enclosed pool. A lake may be navigable in one season and farmland in another, may support floating rather than sinking, or may display phenomena more commonly associated with geysers, storms, or volcanic activity.
Mrs. Loudon gives Niagara’s scale in practical measurements: the Niagara River is 1,650 feet wide and plunges over a precipice 160 feet high. The Horse-shoe Fall is presented as especially astonishing because the water’s force sends it outward in a curved sheet that strikes 50 feet from the base. [17][18]
The most vivid claim is that visitors can walk completely behind the falling sheet without getting wet. The surprise is not only the height of the fall but the shape and trajectory of the water: rather than dropping straight down against the cliff, it projects outward far enough to leave a space behind it.
Across these examples, Mrs. Loudon makes water surprising by emphasizing its independence from ordinary expectations. Tides are regular but shift daily; currents move without wind; the Gulf Stream’s calculated drift spans years and continents; seawater temperatures do not simply follow the air; fresh water can emerge within salt water; the Black Sea combines low salinity with violent storms; lakes can float, disappear, boil, or lie below sea level; and Niagara’s falling water curves outward enough to permit passage behind it. Her method is to turn each natural feature into a practical puzzle, pairing an exact figure or observable detail with a result that seems impossible at first glance.
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