66 Intelligence and Miscellaneous Articles. 



as a special instance of subsidence, the Achensee of a lake lying in 

 a faulted line of dislocation ; L. Alleghe and L. Derborence as lakes 

 formed by Bergstiirze dnring the last century ; the prehistoric delta 

 of the Arve as the most conspicuous instance in the Alps of the 

 partial damming-up of a valley by diluvial detritus ; the quondam 

 Lake of Eeutte as an instance connected with violent inversion of 

 strata ; and the ancient lakes of the Grodner and Oetz Thais as in- 

 stances of the action of moraines. 



The common fact of observation that lakes are more numerous in 

 glaciated than in non-glaciated countries, the author thought, was 

 partly explained by some of the foregoing principles, partly by the 

 better preservation of lake-basins in glaciated countries from silting 

 up and from becoming thus obliterated, while in some glaciated 

 regions lakes are wanting. 



XI. Intelligence and Miscellaneous Articles. 



ON THE EXACTNESS OF THE MEASUREMENTS MADE WITH 

 MERCURIAL THERMOMETERS. BY J. M. CRAFTS. 



ATHEEMOMETEE with a large bulb readily indicates 0°-002 ; 

 but the preciseness of the observation is restricted by slight 

 perturbations caused by variations in the capillary resistance of the 

 stem, by changes of pressure proceeding from barometric changes or 

 owing to the position of the thermometer, and also by calibra- 

 tion-errors and the difficulty of getting a large thermometer to take 

 the temperature of its surroundings. 



Neglecting these errors, the sum of which does not exceed o, 02 

 in suitably arranged experiments, let us examine those which are 

 due to movements of the particles of the glass, slow movements 

 which succeed expansion by heat, and which would involve errors 

 if their effect could not be estimated. Some distinguished physi- 

 cists have compared glass to sealing-wax : according to them, it 

 yields to pressures, and those of the atmosphere and of the air left 

 in the stem determine the changes of volume of the bulb of a ther- 

 mometer. Others, estimating at less the part played by pressure, 

 have cited the case of a bar of metal suspended by its extremities, 

 which slowly becomes permanently deformed. These analogies 

 appear to me fallacious : we have not here to do with pressures 

 similar to the enormous force that causes the bending of a bar ; we 

 ought rather to compare the bulb of a thermometer to a leaden 

 pipe, which nevertheless supports for years the pressure of a high 

 column of water, whilst the least bending deforms it. Person's 

 experiments, moreover, since confirmed by mine, showed that no 

 important influence could be attributed to pressure. 



Numerous determinations tend to prove that we have to do with 

 motions which are but little under the influence of external forces, 

 and that their effects can be foreseen and regulated, by which the 

 precision of thermometric measurements can be considerably 

 augmented. 



