THE EXPERIMENTS OF DR. P. W. BRIDGMAN ON 

 THE PROPERTIES OF MATTER WHEN UNDER 

 HIGH PRESSURE. 



Introductory note by C. (1. Abbot. 



[With 1 plate.] 



We live in a "world in "which the ordinary temperature lies between 

 the freezing and the boiling points of water, and the ordinary pres- 

 sure is that of the atmosphere, or 15 pounds to the square inch. 

 We accustom ourselves to the properties of matter under these cir- 

 cumstances and forget that under others the same substances might 

 behave differently. For instance, we think of water as existing 

 under three forms, steam, liquid, and ice, according as the tempera- 

 ture is a little above normal or a little below what we are accustomed 

 to. We think of mercury as always a liquid which, on account of 

 its very slight volatility, its heavy weight, and its being a fluid 

 metal, though conducting electricity like other metals, is especially 

 valuable in the laboratory, to contain gases, to enclose in ther- 

 mometers and in barometers, and to use for electrical purposes. 

 But if the temperatures prevailing in the laboratory were those of 

 liquid air the mercury would be found to be solid like other metals 

 and perhaps could even be used to make nails of to fasten the 

 laboratory floors. The extraordinary electrical properties of metals 

 at very low temperatures, as found by Dr. Kamerlingh Onnes in his 

 experiments with the gas helium, have been mentioned in this report 

 in an article entitled " The Discovery of Helium and What Came 

 of It." 



The properties of substances of many kinds at enormous pressures 

 have been investigated of late years by Doctor Bridgman, and the 

 following extracts from his published works will give the reader 

 some impression of the difficulties of such research and the extraor- 

 dinary results achieved. 



The value of such researches is increased by the thought that in 

 the formation of the earth materials which compose its crust, includ- 

 ing minerals of many kinds, have been subjected to enormous pres- 

 sures, owing to their burial miles below the surface. Without such 

 laboratory experiments as those which Doctor Bridgman has made 



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