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Ben Franklin

Temple's Diary

A Tale of Benjamin Franklin's Family

In the Days Leading up to The American Revolution

April 15, 1775

I asked Dr. Franklin why he kept measuring the sea's temperature. He was delighted by my question and gave me a whole lecture on that warm current, a kind of river within the sea, that is called the Gulf Stream. For various reasons, it is extremely important for sea captains to map its course. One reason is that if a merchant ship manages to sail on it, it will move along much more quickly, at less expense, and be able to deliver its cargo sooner. The reason some ships take so much longer to cross the Ocean is that they are sailing against the Gulf Stream's current and have to struggle against its strength.

Charting it properly, he told me, is also essential for another economic reason, since whales, in order to keep comfortable in the frigid waters, swim along the edges of the Gulf Stream. Having an accurate chart thus makes it easier for the whaling captains to capture them and extract their precious oil so useful for lighting and a whole lot of other purposes. The existence of this current has been known for a long time but precise information about it is kept secret by the few who are in the know.

The big whaling center, he said, is the island of Nantucket, and since his mother came from Nantucket, he has many relatives over there who are just as eager as he is to learn more about the Gulf Stream.

Would I care to help him? Of course I would. I am becoming so bored that I even miss my French classes with all their tricky genders and irregular verbs. Apart from taking the sea's temperature at various times of day and evening, to verify that Gulf Stream water is really warmer than the sea it runs through, I have to look out for what he calls "Gulf weed" and also take notice of whether or not the water sparkles in the night. Gulf Stream water, says the Doctor, does not sparkle in the dark. And he handed me the chart which I am reproducing here. This is great fun.

of air
of Wats.
April10  62      
 11  61      
 12  64      
 13  65      
 14  65   °     ′°     ′ 
 26 6070   37 3960 38Much gulph weed; saw a whale.
 27 6070S S EW b S 37 1362 29Colour of water changed.
 288 A.M.7064S WW N W 37 4864 35No gulph weed.
 ---6 P.M.6760  34  Sounded, no bottom.
 298 A.M.6371NW4437 2666 0Much light in the water last night.
 ---5 P.M.6572N E 57  Water again of the usual deep sea colour, little or no light in it at night.
 ---11 dit.6666N WbNW b S    
 308 A.M.6470N EW b N69   
 ---126270 E b S2437 2068 53Frequent gulph weed, water continues of sea colour, little light.
 ---6 P.M.6472E S EW b N43   
 ---10 dit.6565S 25  Much light.
May17 A.M.6863  60  Much light all last night.
 ---126556S S WW N W4438 1372 23Colour of water changed.
 ---4 P.M.6456 W b N21   
 ---10 dit.6457S WW N W31  Much light.
 28 A.M.6253  1838 4374 3Much light. Thunder-gust.
 ---126053W S WN W18   
 ---6 P.M.6455N WW S W15   
 ---10 dit.6555N b WW b N10   
 37 A.M.6254  3038 3075 0