G^OPHYSICAI^ LABORATORY. 95 



the thermo-element is certainly in error by more than ten times this amount 

 at the melting-point of platinum. It was therefore deemed necessary to 

 undertake a new investigation of the high-temperature region with the gas 

 thermometer, and in particular to extend its range for a considerable interval 

 above 1150°, in order that a sound basis might be established for the mineral 

 work of this laboratory. 



Accordingly, such an investigation was begun in 1904, and the final results 

 were published within the past year.* It proved possible not only to attain 

 higher accuracy in the region between 400° and 1150°, but to extend the 

 fundamental measurements to 1550°, with an accuracy estimated at 2° at the 

 latter temperature. 



In the meantime, the temperature measurements made in this laboratory 

 with thermo-elements had been interpreted in the old way, by extrapolating 

 the curve of temperature and thermal electromotive force. These results 

 now require to be corrected by the amount of the difference between the old 

 temperature scale and the new, which makes it necessary to recalculate the 

 existing temperature data of this laboratory in terms of the new scale. This 

 paper presents a summary of the values resulting from this recalculation. 



Some of the European students of silicate solutions have encountered 

 difficulties in the determination of mineral melting-points which have led to 

 the belief that most or perhaps all minerals do not melt at a determinable 

 "point," but rather that the phenomena of melting extend through a con- 

 siderable temperature interval. Experimental evidence is here offered, in 

 the case of two of the typical minerals in question, that this uncertainty was 

 merely the result of the experimental method employed. This is a matter of 

 some importance, because the above conclusion, if true, would necessitate a 

 new system of definitions for melting silicates. 



(11) Ein neues petrographisches Mikroskop. Fred. Eugene Wright. Tschermak's Min. 



Pet. Mitt. 29, 489. 1910. 



A German translation of "A new petrographic microscope" (Am. J. Sci. 

 (4) 29, 407, 1910). Reviewed in Year Book No. 9, p. 95. 



(12) The influence of pressure on the melting points of certain metals. John Johnston 



and L. H. Adams. Am. J. Sci. (4) 31, 501. 191 1. 



The authors have been engaged in developing methods and apparatus by 

 means of which it will be possible to investigate the effects of high tempera- 

 tures and pressures on certain systems and reactions, and especially those in 

 which water plays an important part. The work has progressed until now 

 we are able to introduce into the bomb current leads and thermo-element 

 wires in such a manner that the wires are all thoroughly insulated elec- 

 trically, and the joint remains absolutely pressure-tight. Thus, it is possible 

 to heat a substance to somewhat over 400°, under pressures up to 2,000 atmos- 

 pheres, and to measure both temperature and pressure with precision. More- 

 over, the whole system, by reason of the special methods of construction 

 adopted, is absolutely free from pressure leaks, even when the bomb is 

 repeatedly closed and opened, disconnected from, and reconnected with, the 

 remainder of the high-pressure system. For instance, on one occasion heat- 

 ing was continued for 30 hours continuously at a pressure of 1800 atmos- 

 pheres, without sensible loss of pressure in the whole interval. 



* Day and Clement, Am. J. Sci. (4) 26, 405, 1908 ; Day and Sosman, Am J. Sci. (4) 

 29, 93. 1910. R. B. Sosman, Am. J. Sci. (4) 30, i. 1910. 



