BORAX. 29 



Then we tried by various means to recrystallize the melted ortho- 

 clase. We mixed crystalline powder with the glass, we applied suc- 

 cessive quick shocks to the cooling liquid for several hours with an 

 electric hammer below the crucible, we varied the rate of cooling and 

 even tried rapid see-sawing between 8oo and 1300 . We circulated 

 air, water vapor, and carbonic dioxide through the charge throughout 

 the heating, and finally introduced a rapid alternating current sent 

 directly through the substance while cooling, but no trace of crystalli- 

 zation resulted. An extremely viscous, inert mass always remained, 

 which gradually hardened into a more or less opaque glass. It ap- 

 peared somewhat translucent if very high temperatures had been 

 reached, but was never clear. 



Following orthoclase, a number of specimens of natural albite were 

 tried under similar conditions and with entirely similar results. 



Later on, when more experience had been acquired, these minerals 

 were taken up again and a satisfactory explanation for their behavior 

 was found. But for the moment all the defining phenomena ap- 

 peared to be so effectively veiled by some property, presumably the 

 viscosity, that we were constrained to look about for some similar 

 compound which should give us a better insight into the behavior of 

 mineral glasses and their thermal relations, and to lay aside the feld- 

 spars until they could be more successfully handled. 



This outline of our unsuccessful experiences is given here in some 

 detail, in order to show the actual difficulties which confront the 

 student in working with the feldspars, in the face of which it is cer- 

 tainly not surprising that uncertain and contradictory conclusions 

 have been reached. 



Borax. 



The substance chosen for this preliminary work was ordinary 

 anhydrous borax (sodium tetraborate). We chose this merely be- 

 cause it was a simple glass and unlikely to undergo chemical change. 

 It is easily obtainable pure and its thermal phenomena are within 

 easy reach. The study of borax proved to be most instructive. 

 It gave us an effective insight into the behavior of this class of sub- 

 stances, and in particular served to define the phenomena of melt- 

 ing and solidifying in substances which undergo extreme under- 

 cooling and which recrystallize with difficulty, or not at all. The 

 results of this study of borax were, therefore, of much interest in them- 

 selves and were given in a paper before the National Academy of 

 Sciences at its spring meeting in Washington last year (April 21,1 903) , 

 but were not printed at that time. 



