Page:Evolution of the thermometer.djvu/32

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by warming gently the air in the larger bulb

Mersenne's thermometer.

while the smaller was plunged in water and then removing it, a few drops of the liquid rose in the graduated tube forming a short column of water that served as an indicator of changes of temperature. The graduation

A Kircher's thermometer.

of the stem was peculiar; it was divided into eight degrees and these were numbered on one side from above down ward, and on the other in reverse order.

In 1643, the learned Jesuit Athanasius Kircher published a quarto entitled: "Magnes, sive de arte magnetica," in which he mentions several thermoscopes. They have the usual form of the water-air instruments, but one is inverted making it convenient for testing the temperature of liquids. Kircher explains correctly the movement of the column of water caused by the expansion of the air, and adds the instrument indicates the goodness, the mild-