Page:Evolution of the thermometer.djvu/47

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46
EVOLUTION OF THE THERMOMETER.

mencement the degree of cold at which water begins to freeze, or better the temperature of boiling water, so that without sending a thermometer to a distance, one could communicate the degrees of heat or of cold found in experiments and record them for the use of posterity." In this passage Huyghens does indeed suggest the two phenomena for fixing a standard, but only as alternatives, and he seems to have had no idea of dividing the space between them.

The proposition to divide into equal parts the interval between two points to be ascertained by experiment was made four years later by Honoré Fabri, a Jesuit of French birth, who had been one of the corresponding members of the Accademia del Cimento. In his voluminous work on physics published in 1669, he describes an experiment with a Florentine thermometer for the purpose of constructing such a scale; he applied snow in very cold weather to the bulb and marked the point at which the liquid stood, then he marked the position of the liquid at the highest heat of summer and divided the line drawn between these points into eight equal parts. As we now know, the higher fixed point was ill-chosen, but the method was correct in principle, though not adopted until