Copy 1, Volume 2

Outlines of mineralogy, geology, and mineral analysis / By Thomas Thomson.

  • Thomson, Thomas, 1773-1852.
Date:
1836
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of mineralogy, geology, and mineral analysis / By Thomas Thomson. Source: Wellcome Collection.

    23/586 (page 9)
    contrary conclusion from observations, which, however, are far from conclusive. A fortunate accident has demonstrated that the climate of Italy has undergone no sensible alteration during the course of the last two centuries. The Academy del Cimento, which may be said to have terminated its scien- tific labours about the year 1667, contrived a thermometer, which was reduced to Fahrenheit’s scale by Dr. Martine.* In the year 1829, Signor Libri of Florence found a consider- able number of these original alcoholic thermometers of the Academy, and was thus enabled to verify the reductions of Dr. Martine.t By a fortunate accident some registers of the weather kept by Raineri, a pupil of Galileo for 16 years, were discovered. By the discussion of these, with a knowledge of the true scale, Signor Libri has been able to show that no sensible change has taken place upon the climate of Florence between that period and the present, though the contrary had been suspected. { M. Arrago has demonstrated that during the last 2000 years the temperature of the earth cannot have varied so much as 3th of a degree, otherwise the length of the day would have altered, which is not the case. When we dig to a certain depth below the surface of the ground, we come at last to a situation in which if the bulb of the thermometer be put, it remains unaltered during the whole year. The heat at this depth is considered as repre- senting the mean heat of the place at the surface of the ground. The bottom of the cavern under the Observatory of Paris is about 90 feet below the surface of the ground. <A thermo- meter placed in it varies only about Ath of a degree during the whole year from 52°, which is the mean temperature of Paris. Lambert, in his Pyrometry, published in 1779, gives a set of observations made by M. Ott, in a garden near Zurich, in Switzerland. ‘The observations were made with seven ther- mometers, the bulbs of which were sunk respectively 0:266 foot, 0°5325 foot, 1-065 foot, 2°13 feet, 3-195 feet, 4-26 feet, and 6°39 feet under the surface of the ground. The following table exhibits the result of these observations, which were continued for four years :—4 * Martine’s Essays, p. 38. + Ann. de Chim. et de Phys. xly. 354. { Forbes’ Report on Meteorology, p. 209. § Ann. de Chim. et de Phys. viii. 214.