178 REPORTS ON INVDSTI CATIONS AND PR0JB;CTS. 



then similar combinations in which exceptional phenomena occur ; then simple 

 rocks of three components, etc. — the general principle of effective progress 

 being to meet and study the unknown phenomena one at a time. Our studies 

 hitherto have, therefore, been confined to single minerals and to compara- 

 tively stable combinations of two under usual atmospheric conditions. The 

 modified conditions which may be produced by an atmosphere of carbon 

 dioxide, or water vapor under pressure, or by pressure alone, have been taken 

 up only in certain special cases, and their systematic development is dependent 

 upon more favorable laboratory conditions than those now available. 



First of all, a simple type of two-component system in which the com- 

 ponents form an isomorphous series of minerals (the plagioclase feldspars) 

 was carefully studied, then a typical eutectic pair (the lime-silica series), in 

 which we found three eutectic mixtures and two intermediate mineral com- 

 pounds. It was also found possible to discover and locate changes in the 

 crystal form of some of the solid minerals below their melting temperature, 

 even where the heat of transformation was extremely small. Such changes 

 fall into two general classes, one in which the change is reversible and one 

 in which it is not. We have been able to locate successfully a number of 

 cases of the reversible change, and during the past year have encountered 

 and successfully solved a problem in which a mineral compound (magnesium 

 metasilicate) appeared in four different crystal forms in irreversible relation 

 to each other, i. e., three of the forms could be changed into the fourth by 

 heating, but the reverse change does not occur. 



This last investigation yielded one fact of a somewhat unusual character. 

 We have been accustomed to think of the laboratory of nature as possessing 

 one great advantage over any effort put forth by man ; with nature we have 

 assumed that there must always have been plenty of time for natural processes 

 to go on to completion. And yet we found that the particular form of this 

 magnesium silicate which is common in nature (enstatite) is not the stable 

 form; the process was rarely carried through to the end in nature's labo- 

 ratory. In meteorites we occasionally find this silicate in its final form. 



In our work on the properties of silica we also found a way to make 

 "quartz-glass," a material of such peculiar properties that it would no doubt 

 be most useful in our everyday life. It differs from other glass but little in 

 appearance, but can be heated to dazzling whiteness without melting, and 

 then plunged into cold water with little danger of breaking. The high tem- 

 peratures required, of course, make it difficult and expensive to prepare. 



Another discovery which we made in connection with the same series of 

 minerals (lime-silica) was very important and somewhat surprising. The 

 peculiar and valuable properties of Portland cement have been commonly 

 attributed to the presence of tricalcic silicate, but we found abundant proof 

 that no such compound exists. It is not unlikely that the continuation of 

 these investigations, which is now in progress, will reveal the true constitu- 



