153 Geological Society : — 



Zincacetimide. 



[Zn. 



AcetamiJe and zincethyle act upon eacli other very violently ; a 

 lare;e cjnantity of gas is evolved, wliich nnalysis proves to be hydride 

 of ctliyle. Zincacetinude is contained in the residue as a white, amor- 

 phous, pulverulent solid, which is reconverted into acetaraide by 

 contact with water. 



These reactions establish the fact, that by the action of zincethyle 

 one of the atoms of hydrogen, in ammonia and analogous nitrogen 

 compounds, combines with ethyle and becomes replaced by zinc. It 

 will be interesting to extend this reaction to the nitrjdes, especially 

 such as contain electro-negative radicals of the othyle familj'^, since we 

 maj' thus expect to obtain a new series of double radicals, amongst 

 which the ketones will perhaps find a home. 1 hope soon to lay the 

 results of this extension of the investigation before the Royal Society. 



GEOLOGICAL SOCIETY. 



[Continued from p. 7S.] 

 December 2, 1857. — Col. Portlock, R.E., President, in the Chair. 

 The following communication was read : — 



" On some peculiarities in the Microscopical Structure of Crystals, 

 applicable to the determination of the Aqueous or Igneous Origin of 

 Minerals and Rocks." By H. C. Sorby, Esq., F.R.S., F.G.S. 



In this paper the author showed, that, when artificial crystals are 

 examined with the microscope, it is seen that they have often caught 

 up and enclosed within their solid substance portions of the mate- 

 rial surrounding them at the time when they were being formed. 

 Thus, if they are produced by sublimation, small portions of air or 

 vapour are caught up, so as to foi^m apparently empty cavities ; 

 or, if they are deposited from solution in water, small quantities of 

 water are enclosed, so as to ioxm fluid-cavities. In a similar manner, 

 if crystals are formed from a state of igneous fusion, crystallizing out 

 from a fused- stone solvent, portions of this fused stone become 

 entangled, which, on cooling, remain in a glassy condition, or 

 become stony, so as to produce what may be called glass- or stone- 

 cavities. All these kinds of cavities can readily be seen with suitable 

 magnifying powers, and distinguished from eaph other by various 

 definite peculiarities. 



From these and other facts, the following conclusions were de- 

 duced : — 



1. Crystals containing only cavities with water were formed from 

 solution. 



2. Crystals containing only stone- or glass-cavities were formed 

 from a state of igneous fusion. 



3. Crystals containing both water- and stone- or glass-cavities 



