Illustration of Newton scale

1701 Newton scale

The book of science

Tom Sharp

Isaac Newton thermometry Illustration of Newton scale

Newton scale

Newton had been appointed master of the mint and was interested in the melting points of metals. Measuring the expansion of linseed oil starting from zero the freezing point of water passing through thirty three the boiling point of water to the melting point of tin but after this linseed oil is too volatile so Newton measured how long it took to solidify after melting on red-hot piece of iron and correlated that time with his measurements for tin deriving eighty one the melting point of bismuth and ninety six the melting point of lead.

Lessons of alchemy

The sun, gold, the moon silver, Mercury mercury, Venus copper, Mars iron, Jupiter tin, Saturn lead, and Neptune bismuth, dialed to the zodiac, were metaphors for the secret keys for the creation of the Philosopher’s stone. Salt is the spirit; sulfur is the soul; and mercury is the body.

Multiple instruments

No one thermometer design can measure all temperatures. Mercury freezes; oils vaporize. Even pure substances may have non-linear rates of expansion especially at the ends of their ranges. A mother puts a hand on her child’s forehead, squeezes a drop to a wrist from a bottle of milk, smells olive oil smoking in a pan, hears water boiling on the stove, the sound of rain and wind, the periodic note of a distant foghorn, wind piercing a coat, drops glinting from icicles melting on an eave.

The Newton scale is not linear; Newton underestimated temperatures above the melting point of tin. Bismuth, for example, would melt at 168 °N if the scale were linear.

See also in The book of science:

Readings in wikipedia:

Other readings: