458 



Scientific Proceedings, Royal -Dublin Society. 



The meldometer therefore, owing to the rapidity of its temperature-rise, 

 should indicate higher fusion-points with minerals than those yielded by 

 other methods, whereas the contrary is found to be the case, and moreover, the 

 discrepancy in this direction should be accentuated owing to " the cohesion of 

 some minerals at high temperatures which may permit of the liquefaction of 

 a crystal without visible optical change." 



The foregoing considerations have led various workers to somewhat 

 discordant results. Doelter's later investigations^ on some minerals which do 

 not show much retardation in temperature-rise, and hence, according to him, 

 are best treated subjectively, are in accordance with those obtained for the 

 same minerals by Joly and Cusack (loc. cit,.). The conclusions of these 

 observers are at variance with those of the workers in the Geophysical 

 Laboratory at Washington, obtained by a non-subjective method, and 

 supported in four cases by the meldometer.^ 



These results are arranged in the following table' : — 



It will be seen that the data of Joly and Cusack are in good agreement, 

 and the results of Cusack on seventeen other minerals are so close to those of 

 Doelter as to suggest that the corrections applied by the latter to some other 

 minerals between 1902 and 1908 would bring them into complete harmony. 



In order to compare the above results with those presented in this paper, 

 a number of experiments were carried out by me on the meldometer, using the 

 foregoing minerals, and the figures of Cusack were substantiated. The wide 

 temperature-interval between, say, melting Palladium (1549) and Wollastonite 



' Zeit. Elektrochem., vol. xii, 1906, p. 617. 



^ Douglas, Quart. Journ. Geol. Soc, vol. Ixiii, 1907, p. 145. 



^ See also Day and Allen, Anier. Jour. Sci. (4) vol. x, 1905. 



* Corrected approximately to recently published standards. 



' Rapid fusion. 



•^ Taschenb. Min. Mitth. vol. xxi, 1902, pp. 23-30. 



