ABOUT THERMOMETERS.

King Country Chronicle, Volume V, Issue 321, 17 December 1910, Page 2

ABOUT THERMOMETERS.

Gabriel Fahrenheit, in 1709, in his laboratory on a very cold winter day experimented in Prussia by putting snow and salt together, and found that the admixture produced a degree of cold equal to the temperature of the outer air. Fahrenheit was so struck with the coincidence that he hastily concluded that he had discovered the lowest degree of temperature known in the world, either artificial or natural. He called the degree zero, and constructed a thermometer or rude weather glass, with a scale graduating up from zero to boiling point, which he numbered 212, and the freezing point 32, because, as he thought, mercury contracted tin thirty-second of its value on being cooled down from the temperature of freezing water to zero, and expanded one hundred and eightieth on being heated from the freezing to the boiling point. Time showed that this arrangel rnent was anything but truly scientific. But Fahrenheit's thermometer had been widly adopted with its in convenknt scale, and none thought of any better until his name became an authority. Then habit made people clirif; to the established scale. The three countries which follow Fahrenheit are England, Holland, and America. Russia and Germany use Baumer's thsmometer, in which the boiling point is counted eighty degrees above freezing point. France uses the centigrade thermometer, so called because it marks the boiling point one hundred degrees from freezing point. On many accounts the centigrade system is the best, and the triumph of convenience will be attained when zero is made the freezing point, and when the boiling point is put 100 or 10000 degrees from it, and all the subdivisions are fixed decimally. If Fahrenheit had done this at first or even if he had made it one of his many improvements after the public adopted his error, the luck of opportunity, which was really his, would have secured to his invention the patronage of the whole world. When any new thermometer is

taken to one of the great observatories for standardisation, it is first handed to a skilled operator, who | takes it to the testing-room. There it is dipped into a vessel filled with a compound far below the freezing point. It is thrust in at the point where it happens to be at the time, and worked up and down until the degree of the compound is reached. Having then recorded the lowest temperature, the process of testing it for the highest is begun. This is just as simple as testing for the low temperature. The bulb is dipped into a vat 01 water, first to 60 degrees. Then it is worked gradually until 130 degrees is reached, If the mercury in the bulb will indicate J.ao degrees further testing is unnecessary, because that is a tolerably warm temperature, and one seldom, if ever, reached bv natural heat. A thermometer the bulb of which contains mercury will not register below 28 degress below zero ; that is to say, mercury will freeze at that point. Of course, in this country little practical use is found for a thermometer showing more than 28 degrees below zero, but in the Arctic or Antarctic they are essential. Such instruments, however, contain spirit; in the bulbs instead of mercury ; but even this fluid becomes sluggish when 40 or 50 degrees below zero is reached, and it will seldom show 60 degrees below.