420 H. A. Miers — Quartz from North Carolina. 



It is easily conceivable that the action of shearing stress 

 should be enormously greater than that of simple pressure. 

 For it seems probable that pressure can only cause decomposi- 

 tion when the resulting product is more dense, has a greater 

 specific mass, than the original substance. With shearing stress 

 the case is altogether different. All matter is in a state of 

 vibration and it is easily conceivable that the forcible friction 

 of a hard substance may increase vibration in somewhat the 

 same way as does a bow drawn over a stretched cord. Both 

 the elasticity and the tension of the atoms themselves are 

 vastly greater than those of any stretched cord so that the 

 increased vibration may easily be sufficient to shatter the mole- 

 cule. 



The transformation of light, heat, and electricity into mechan- 

 ical energy as well as the converse transformations are extremely 

 familiar. That mechanical energy may be transformed into 

 chemical energy is proved by the results in these papers de- 

 scribed. The converse transformation, that of chemism into 

 work, is in an industrial point of view by far the greatest 

 chemical problem now waiting for solution. But it is by no 

 means certain that such a transformation is practically possi- 

 ble. At least it seems probable that the improvement in our 

 method of obtaining work from the chemism of carbon may 

 be in the direction of substituting electricity for heat as the 

 intermediary. 



Art. LVI. — Quartz from the Emerald and Hiddenite Mine, 

 North Carolina; by H. A. Miers 



The remarkable crystals of quartz from this locality have 

 been the subject of several memoirs by the late Professor Gr. 

 vom Rath, which render it unnecessary to say anything regard- 

 ing the general features of the North Carolina quartz. The 

 following note, which relates to three interesting crystals 

 recently presented to the British Museum by Mr. W. E. 

 Hidden, serves to confirm and supplement the observations of 

 vom Rath, concerning the rare planes which occur upon some 

 of the more highly modified crystals from the Hiddenite mine. 

 In the accompanying diagrams the crystals are drawn and let- 

 tered in accordance with the position and notation adopted by 

 vom Bath in order to facilitate reference to his figures. 



Crystal No. 1 is remarkable as showing a very well devel- 

 oped basal plane (fig. 1) ; the crystal is a pyramid II, — R, 

 broken at its lower end so that no prism faces are visible; the 



