118 The Ottawa Naturalist. 



Naumann's definition of a crystal is a very concise and satisfactory 

 one. It is this : " Any rigid inorganic body possessing an essential and 

 original (primitive) more or less regular polyhedric (many-sided) form 

 which is directly coniiected with its physical properties." 



This latter clause of the definition is very important as explaining 

 why cleavage fragments, pseudomorphs &c are not to be termed 

 crystals. 



To the question why calcite, for instance, should assume one form 

 of crystal, and garnet another, science can return no answer, but must 

 content itself with determining and describing these curious and multi- 

 farious forms. 



The word -crystal" is derived from the Greek word '-/cpuffraXXo^" 

 meaning " ice". The ancients first give this name to the variety of 

 quartz which we call " Rock-crystal, " because, from its transparency, 

 its usual freedom from color, and the way in which it was found to en- 

 close other bodies, they iraigined it had been formed by the action of 

 intense cold on water, which thus becime extraordinarily hardened. 



The name was later transferred to pure transparent stones, such as 

 were after used for seals and engraved gems. 



Some of the old writings on this subject are very amusing. Albertus 

 Magnus, in the imdJle of the 13th century, gravely relates how the 

 intense cold on the summits of some lofty mountains dries the ice so 

 thoroughly that it becomes crystal. Even as late as 1672 the 'learned 

 Robert Bjyle goes into a long dissertation to prove that crystal could 

 not be ice, adducing as two of the strongest proofs of this, first, the fact 

 that ice floats on water and crystal does not, and, secondly, that Mada- 

 gascar, India, and other countries in the torrid zone, abound in crystal, 

 and he could not believe tint any ice, however hard, could withstand 

 the heat of those countries. Later the term "crystal" was applied to 

 any mineral naturally limited by plane faces. 



It was not until 1669 that any important discovery 

 re-arding the properties of crystals was made, and then it 

 was thu Nicolaus Steno, a Danish physician, discovered for the 

 first time the constancy of angles in Rock-crystal. But it is generally 

 admitted that Ste.no himself did not fully grasp the importance of his dis- 



