James Watt’s notebook
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The papers of James Watt, held in the Library of Birmingham, include a number of his experiment notebooks. They show that Watt’s enquiring mind continued to remain curious about the world around him. His experiments on the possibilities of steam power were meticulously documented up until his death in 1819.
Transcription:
10. I found that the quantity of water used for injection in fire engines was much greater than I thought was necessary to cool the quantity of water contained in the steam down to below the boiling point. I mixed 1 part of boiling water with 30 parts of cold water I found it only heated to the arithmetical mean betwixt the two heats & that it was scarcely sensibly heated to the finger.I took a bent glass tube & inserted it into the nose of a tea kettle the other end being immersed in cold water. I found on making the kettle boil that tho there was only a small increase of the water in refrigeratory that it was became boiling hot. This I was surprised at and on telling it to Dr Black & asking him if it was possible that water under the form of steam could contain more heat that it did when water it was heated to 212° or boiling hot it would receive no more heat tho the fire & it continued the same that the steam that go off do not appear sensibly hotter to the thermometer than 212 & that the quantity of water that is evaporated in a minute is small in proportion to the heat that is certainly added to the water.
The thought that these steams certainly carried off or contained more heat than was sensible to the thermometer & that in certain circumstances they might part with their heat to other bodies.
He accordingly took a common still and having put a quantity of water into it he adapted a refrigeratory as usual this he filled with a measured quantity of water of a known heat he then distilled till there came into his receiver a certain proportion of the water contained in his refrigeratory he found the water (alchemical symbol for water - inverted triangle) in the refrig. had acqu...
Reference: James Watt Notebook, 1765-1814 (MS 3219/4/170)
