342 THE DIAMOND AND OTHER PRECIOUS STONES. 



Oil this pearl ?" asked Philip II of au eastern merchant. " Sire, I knew 

 there was in the world a King- of Spain to buy it." 



Thus far we have said little for science in tbis dissertation, and yet 

 precious stones, and, in general, all crystals, from their geometrical 

 forms, their chemical and mechanical properties, their weight, their color, 

 their action on light, and their electrical qualities, tbey all olfer the most 

 delicate as well as interesting applications of the principles of pliysics. 

 Hatty conceived a crystal to be made up of an assemblage of minute 

 parts or molecules, each having the same definite form. From a few of 

 these elementary molecules, which he called primary forms, he was ena- 

 bled to build u}) all the forms which occur in nature, and in so doing he 

 was led to inquire whether the same elementary forms might not give 

 rise to more than one derivative form, or, in other words, whether the 

 same substance could not crystallize in more than one form. Nature 

 replied that she had anticipated his question by producing a specimen 

 of the anticipated form. By the application of mathematical analysis 

 to the fertile conception of Haiiy all the forms of crystals which can 

 Ijossibly be produced by an aggregation of a given elementary form, as 

 well as the forms which are incompatible with a i)articular elementary 

 molecule, can be foretold, and these predictions are, in all cases, found to 

 be in exact accord with the actual facts of observation 5 while the 

 chemist and the mineralogist are continually adding to the list of crystals 

 of theoretically possible forms, in no case has one been obtained of an 

 a priori incompatible form. 



Hardness is an important quality by which valuable stones are 

 distinguished. In the cutting of the Koh-i-noor it was found that it 

 required a whole day to produce facets which could be commonly formed 

 in the course of three hours. It was also found necessary to increase tlie 

 rapidity of the rotation of the wheel on which the diamond powder is 

 spread. In an experiment made some years ago at the expense of the 

 Institute, a black diamond of Borneo was put in the hands of Gallais, 

 tlie diamond-cutter. On this he wore out a steel wheel and a large 

 quantity of ordinary diamond powder without making the least impres- 

 sion on its surface. It lost none of its roughness, although loaded with 

 a considerable weight, and heated almost to whiteness by the rubbing 

 of the wheel, which revolved with such velocity as to emit a continual 

 shower of sparks during the operation. 



This intractable substance required the i)ov;der of black diamonds, 

 like itself, to produce the desired eU'ect, and doubtless some day the 

 ])owder of black diamonds will be used to advantage in cutting the ordi- 

 nary diamond as well as in other processes of the arts. Every one has seen 

 a glazier, with a minute point of a diamond, trace upon glass an almost 

 imperceptible groove in the crust of the glass, which renders it easily 

 frangible in a given direction. It is conjectured by some that the an- 

 cients in engraving on sapphires and rubies have used a diamond point 

 as a burin, and the finish of some parts of cameos and intaglios deeply 



