168 ANNUAL KEPOKT SMITHSONIAN INSTITUTION, 1925 



Apart from the various effects which have been measured ac- 

 curately, results obtained under hi<ih pressures suggest other new 

 points ol' view. Thus in the j^reliniinary work, before I had found 

 out how to make tight joints, or had learned what the capabilities 

 of steel cylinders were in withstanding pressure, I observed a number 

 of different types of rupture under unusual conditions, which are of 

 some interest to the engineei-. By selecting results under different 

 conditions, it was jwssible to vshow that none of the ordinarily 

 accepted criteria of rupture ai-e valid except under restricted circum- 

 stances. The general, and therefore the significant, conditions of 

 rupture are yet to be formulated. 



Finally, Ave may glance at what remains to be done. Although 

 the most readily obtainable results have been secured, the subject has 

 not been more than begun. It becomes more and more impressed 

 upon me that significant results are to be found in little frequented 

 places, as, for instance, bj^ working on materials that have extreme 

 properties or in going to extreme temperatures. Thus, quite recently, 

 this has led me to determine the properties of ctesium, the most com- 

 pressible of the metals, with the extremelj' suggestive discovery of 

 minimum resistance. The same sort of thing is to be done with 

 many other materials of unusual properties. The extension of these 

 high-pressure results to temperatures near the absolute zero, where 

 phenomena assume an unwonted simplicity because of the absence 

 of temperature agitation, will doubtless be of extreme importance. 

 Results just as important lie also at high temperatures, a most 

 difficult field, which the Geophysical Laboratory is skilfully 

 attacking. Interesting special results ma}^ be found ; the will-o'-the- 

 wisp of manufactured diamonds is always before us. Without 

 doubt, important practical developments lie in a field as yet 

 practically untouched, that of organic, colloidal, and biological 

 chemistry. It was shown a long while ago, at the West Virginia 

 Agricultural Ex])ei'imont Station, that high pressures will sterilize 

 milk. I have found that high pressures in the cold will also coagu- 

 late egg white, or the proteids of meat. Here is an enormous field 

 untouched. V\'e ought to know the effect of pressure on every sub- 

 stance of biological significance, just as we now know the effect of 

 an elevation of temperature, and we ma}^ anticipate that important 

 changes or combinations may be produced by pressure, just as thej' 

 are now produced by temperature. 



On the pureh' physical side, the field is immense. Entirely apart 

 from new experimental knowledge, we can not be satisfied with any 

 theory which does not adecpiately explain the effects of high pressure 

 already known, and conversely I venture to hope that these i)he- 

 nomena of high pressure may play an increasing part in formulat- 

 ing more adequate theories of the structure of matter. 



