

167 



Ception in the behaviour of the individuals which h;tvt- a part in it. 



llo\vv\vr on closer examination, this appears to be by no means 

 the ease under all circumstances. In this well-governed society too, 

 with its clear lines of demarcation and its strictly defined distinction 

 i^M-s and systems, there are a number of individuals which 



have certainly not as they should do. Numbers of eccentricities 



v to be noted, and the somewhat revolutionary manifestations 

 of many individuals take place here in a similar degree, as in our 

 much more insufficiently ruled human society. 



In the present chapter we propose to deal with some of tin 

 j'hrnomena indicated, and as experience has taught that even these 

 crystallographical eccentricities conform to certain well determined 

 laws, let us see first, what remarks and attempts at an explanation 

 of the peculiar behaviour of these eccentric individuals, have been 

 made up till now. 



2. Since Rome de 1'Isle and Hauy, it has been stated by 

 several observers that many crystals have a strong tendency to 

 form more or less complicated aggregates. This fact has been met 

 with innumerable times especially among minerals, and of some 

 of them this tendency seems to be so characteristic, that separate 

 crystals of such minerals must be reckoned among the greatest 

 mineralogical rarities. 



Whether crystals will deposit from a solution as separate indivi- 

 duals, or as a confused aggregation of irregularly situated crystals, 



ms to be determined by special circumstances of deposition- 

 velocity, and 'by the fact that crystallisation may take place quietly 

 or not. Indeed, if the solution be strongly agitated or irregularly 

 moved during the process of crystallisation, an aggregate of small 

 crystals directed towards all sides is commonly the result. Such 

 crystal-aggregates may be completely irregular: a heap or a crop 

 of arbitrarily grown needles or plates will be present, and no definite 

 relation whatever will exist between the mutual orientation of 

 two contiguous individuals. Often however a great number of small 

 crystals, if they are even only rudimentary or embryonic (trichites, 

 crystallites, etc.), -- combine in a perfectly regular way according 

 to definite laws. In such cases more or less symmetrical groupings 

 result, of which the well-known swoze'-crystals x ) (fig. 132} are most 



1) G. Nordenskjold, Bull, de la Soc. Miner. 16. 59. (1893); 17. 141. (1894); 

 L. Bombicci, Bull, de la Soc. Miner. 8. 85. (1880). 





