cylinder was marked "greatest cold" (0° F.), and from this to the upper end were 24 degrees, some bearing special names; the fourth was "very cold," the eighth "cold," the twelfth "moderate," the sixteenth "warm," the twentieth "very hot," and the twenty-fourth "unbearable heat." The second tube of Wolf differed little in size. Wolf tested the two instruments and found the slight difference between them of one-four hundred and sixteenth of the entire scale.
Another friendly contemporary of Fahrenheit, Dr. Hermann Boerhaave, has recorded in his "Elements of Chemistry" some particulars of the celebrated thermometers. Boerhaave, writing in 1731, ascribes the invention of the thermometer to Drebbel, cites Amontons, Mariotte, and others, and gives an account of a noteworthy experiment made by Fahrenheit, who poured spirit of nitre on ice and got a temperature of −29° F., using an instrument graduated to −79°. Boerhaave then describes "an elegant thermometer made at his request by the skilled artist Daniel Gabriel Fahrenheit" thus: "The lower cylinder of this instrument contains 11,124 parts of mercury, which in the utmost cold observed in Iceland reached to the
