J. C. W. Ilumfreji. 
Fig. 18. Same after 20 minute.^ at fio ('. 
Fig. 19. Same after 40 miimte.s at GO O'. 
1 rnyis.. 
./, rol. 200 , Plate . 1 . 
Fig. 20. .'tingle crystal after stiaiiiiiiig 
in tonsil 111 and re-etcliing x .1. 
Fig. 21. Same after cooking for 20 miimte.s 
at loo C. and re-etching. 
ih'g. 22. A .single crv.stal after strain¬ 
ing in tension and re-etching x 4. 
Fig. 2.3. Same after .'I weeks at atnios. 
teni]). 
Fig. 24. A single crystal after strain¬ 
ing in tension, cooking 2 hours at 
100 C'.. and re-etrhing. 
