Page:Evolution of the thermometer.djvu/74

 mark 0 from whence the further degrees of heat are computed upwards. Now if this be immersed in a vessel of water gradually heated, the mercury will be found to ascend continually till the water comes to boil, at 212° or more; so that setting aside the dilatation of the glass it now possesses 11,336 spaces of which in the greatest cold it possessed 11,124, so that by this difference of heat the bulk is dilated to

In another passage, Boerhaave relates that on comparing two of Fahrenheit's thermometers, one of alcohol and one of mercury, he found a slight discrepancy and reported it to the maker, who "ingeniously owned the failing, but did not then see the cause of it, but revolving it in his own mind he at length discovered that the very glass made in Bohemia, England, and Holland expands more or less easily by the same degree of heat," and Fahrenheit suggested that the two instruments ought to be made of one kind of glass. Thereupon the doctor adds this comment: "How circumspect does nature require us to be in order to discover truth in physical matters, and how often are we deceived by following a general rule."