c<&' W. Hallock—Flow of Solids. 27T 



Art. XXXII. — The Fioiv of Solids:* or Liquefaction by Pres- 

 sure; by William Hallock. 



The question before us is this : Can solids be liquefied by 

 pressure alone, without a rise of temperature? Also, is chemi- 

 cal action possible during this enforced liquid state? Applied 

 to rocks and rock-making magmas it becomes a question of the 

 first importance to geologists; as such it has been frequently 

 discussed theoretically, but has seldom been experimentally in- 

 vestigated. 



Walter Spring seems to be the pioneer in these tests, having 

 published very many results during the past few years, f His 

 memoirsf would seem to have proved bej^ond doubt that press- 

 ures under 7000 atmospheres will liquefy most solids,^; and that 

 it is only a question of slightly higher pressure to liquefy nearly 

 all. He also finds that chemical action takes place under these 

 circumstances,t at least where the volume of the product is 

 less than that of the original materials. Unfortunately, or 

 fortunately, our confidence in Mr. Spring's conclusions is seri- 

 ously shaken by the criticisms of Ch. Friedel§ and Ed. Jan- 

 nettazj who were not able to reproduce the results given. 

 Henri Tresca^f carried out many striking experiments upon the 

 flow of solids, but did not touch the question of their liquefac- 

 tion. 



In order that I may not be misunderstood, I wish, as far 

 as I am concerned, to give definite meanings to certain 

 terms. Primarily I wish to distinguish sharply between 

 causing a body to flow, and making it a true liquid. Any sub- 

 stance may flow when the forces acting to cause the mole- 

 cules to change their relative positions is greater than that tend- 

 ing to hold them in their original positions; that is, greater than 

 the rigidity of the substance. Two causes may then produce 

 a flowing, an increase of the disturbing force, or a diminution 

 of the resisting power, the rigidity of the material. Pressure 

 may act as the first of these causes, and heat, the second. 



* This is an abstract of a paper in the Bulletin of the Geological Survey, Chemi- 

 cal Division, for 1886-7, which is itself compiled from a report made September 

 9th, 1885, to the director, .J. W. Powell, under whose direction I undertook this 

 work, and by whose kind permission this abstract is published. 



f W. Spring. Bull, de l'Acad. R. de Belg., II, xlix, 1880, and III, ix, 1885 ; 

 and Bull, de la Soc. Chem. de Paris, xxxix, 1883. and xlvi, 1886. 



X W. Spring. Bull, de l'Acad. roy. de Belg., II, xlix, 1880. 



§ Ch. Friedel. Bull, de la Soc. Chem. de Paris, xxxix, 1883. 



|| Ed. Jannettaz. Bull, de la Soc. Chem. de Paris, xl, 1884. Bull, de la Soc. 

 Mineral, de France, viii, 1885. 



If Henri Tresca. Mem. de l'lnst. Savantes Etranges, xvjii, 1868. Comptes Ren- 

 dus, Ixvi, 1868; Ixviii, 1869. 



