File:Transactions of the American Philosophical Society (1793) (14780316201).jpg

Identifier: transactionsofam31793amer (find matches)
Title: Transactions of the American Philosophical Society ..
Year: 1793 (1790s)
Authors: American Philosophical Society
Subjects:
Publisher: Philadelphia : The Society
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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bove water, is warmerthan that over thofe which admit deep water between themand the coaft; but ftill it is colder than the adjacent fea. 5. The water within capes and rivers does not followthe above rules; it being lefs agitated, and more expofedto the heat of the fun, and to receive the heat from the cir-cumjacent land, muft be colder or warmer than that infoundinp;s without, according to the feafons, and tempe-rature of the atmofphere, 6. The paflage, therefore;from deep to fhoal water maybe difcovered by a regular ufe of the thermometer, beforea navigator can fee the land; but as the temperature isrelative, no particular degree can be afcertained as a rule,and thejudgement can only be guided by the difference.Thus in Auguft I found the water off Cape Cod to be 58^by Fahrenheit, and at fea it was 69^; inOdoberthe wa-ter off Cape Cod was 48^, and at fea it was 59^*. Thisdifference was equally a guide in both cafes, though ttebeat was different at different feafons. I /-/- ./.■/.j:
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MARITIME OBSERVATIONS. 85 I do not prefume to fay what is the caufe of this differ-ence of heat between the fea and bank water, but if a na-vigator were to obferve it when near an Ifland of ice, hewould very naturally fay that the ice conduced the heatfrom the circumjacent water, and left it colder than thatat a diflance. And as it is well known that ftones andfand are great condud:ors of heat, it feems probable thatbanks alfo conduct the heat from the adjacent water, thoughnot fo rapidly as the ice. The heat of the water may in-deed be fuppofed to feek its equilibrium, but as long asthe lilands of ice and banks continue to conduct, theremuft be fome difference, and this it is, which, by attenti-on, maybe made a faithful fentinel to give an alarm whendanger is near. I have thought it my duty to prefent my journals as theyw-ere Vv-ritten at fea, to avoid the fufpicion of having addedany thing from the fuggeftions of the imagination. Whilethis will be received as a circumffance favourab

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