Page:Evolution of the thermometer.djvu/18

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17
GALILEO'S OPEN AIR-THERMOMETER.

my invention, or rather of my improvements. But since, as you write to me, and as I steadfastly believe, you are the first to discover and make the instrument, I suppose that those made by you and your excellent workmen are superior to my own; therefore I beg you at the first opportunity to write to me how you have them made, and I will report to you more or less of what is happening here."

In a long letter to Galileo, written 11 April same year, Sagredo mentions the use of wine as well as of water in the thermometers, alludes to having them made at the glass works in Murano, near Venice, and describes the construction of the best and most perfect of his instruments. This was made of a glass tube a finger wide joined to a bulb having a capacity of "three or four drinking glasses;" having made three of different sizes he watched their behavior during one year, sometimes as often as eight times a day, and he expresses wonder at their close agreement in both the extremes of cold and heat, the difference between them being not more than two or three degrees. He expresses surprise also at the great delicacy of his thermometers, which showed a difference of temperature when moved from the interior