140 CARNEGIE INSTITUTION OF WASHINGTON. 



slides and much interest and some surprise were shown at the presenta- 

 tion of the world's volcanism as a constructive rather than destructive 

 agency. Papers are begun on the subjects of the great Vesuvius erup- 

 tion of 1906, the Stromboh outbreaks of 1907, 1912, and 1915, the 

 recent descents into the crater of Vesuvius, the influence of open and 

 closed volcanic conduits on external eruption. 



Astronomy. — The telescopic study of the lunar craters — begun with 

 the 5-inch reflector — just before the war has been interrupted by the 

 inadvisability of using the telescope on the terrace during present 

 conditions, but the total lunar eclipse of July 4 was an event for which 

 to take risks, and perfect weather gave opportunity for very good 

 observation. My notes, in French, are to be published in the Bulletin 

 of the Soci^te Astronomique de France. One of the observed effects 

 brought out a reference to the phenomenon of the ''flashing arcs" 

 observed by me at Vesuvius and Etna. From some recent observa- 

 tions at the front in France, it would seem that sound waves from 

 heavy cannonading have, under certain conditions of hghting, been 

 visible. 



PUBLICATIONS. 



Brief reviews of the papers published by members of the Laboratory 

 staff during the current year follow: 



(1) Some aspects of recent high-pressure investigation. John Johnston. J. Franklin 

 Inst., 183, 1-32 (1917). 



There has been an increasing realization of the necessity of investigating the 

 behavior of substances throughout a wide range of conditions — temperature 

 and pressure especially — if we are to increase the scope of our present chemical 

 generalizations. Considerable work has now been done in the high-tempera- 

 ture field, but until recently very little has been definitely ascertained as to the 

 precise effects of high pressures. Pressure and temperature are completely 

 analogous as variables ; experiment has sho\vn that in general a pressure change 

 of 1,000 atm. will produce no larger effect than a temperature change of a few 

 degrees — a difference which, of course, depends only upon our system of units. 



Pressure raises the melting-point of solids ("with two known exceptions, 

 ordinary ice and bismuth) , the change being successively less with each incre- 

 ment of pressure ; ]3ut there is no evidence at all for a maximum melting-point 

 or for a critical end-point. Indeed, all evidence indicates that by the applica- 

 tion of sufficient pressure gases would be transformed to solids, a conclusion 

 which is in harmony with that reached on other grounds that the interior of 

 the earth is solid. The effect of pressure upon solubility, and upon condensed 

 systems generally, is small; when a gaseous component is present the effect 

 may be very large by reason of the great increase in concentration of the gas 

 produced by the pressure. But many of the effects which have been attrib- 

 uted to pressure are not due to it alone, but often to the high temperature 

 chiefly, the pressure being merely a subsidiary influence; and in such dis- 

 cussion one must always be careful to distinguish between uniform pressure 

 and non-uniform compression, as the latter Avill produce effects very different 

 from those of the former. 



