NA rURE 



[July 2, 1896 



possess no individuality there is also no progress, and it is 

 absurd to look for any development among ores, and stones, and 

 rocks. That, however, is not so obvious. 



Individuals exist in the mineral kingdom just as truly as they 

 exist among animals and plants ; each crystal is a distinct 

 individual, capable of growth by itself, and independent of its 

 fellows ; each pursues its own existence ; it is even in a sense 

 capable of multiplication, for if a crystal growing from solution 

 be broken in two, each half continues to grow as a distinct 

 individual resembling in all respects the parent crystal. 



Mutilate a growing crystal by breaking away one of its 

 corners or edges, it will heal the fracture, restore the missing 

 fragment, and become again a perfect crystal ; thus asserting its 

 individuality in an even more persistent manner than many a 

 living organism. The experiment is one which may easily be 

 performed with a crystal of alum. 



Hence if a definition of life, or a distinction between organic 

 and inorganic be based upon individuality, as it often has been, 

 it will be exceedingly difficult to exclude crystals. This is 

 precisely what many philosophical writers have found. One or 

 two examples will suffice. 



Schopenhauer, for instance, after stating that " in the 

 inorganic kingdom of nature all individuality disappears," is 

 oljliged to confess that " the crystal alone is to be regarded as to a 

 certain extent individual" ; " in the forming of a crystal we see 

 as it were a tendency towards an attempt at life. " Having made 

 this admission he goes on to say : ' ' The crystal has only one 

 manifestation of life, crystallisation, which afterwards has its 

 fully adequate and exhaustive expression in the rigid form — the 

 corpse of that momentary life." There is a constant tendency 

 among philosophical writers to suggest that this individuality 

 implies some relationship between life and crystallisation. 



To take another illustration : St. George Mivart says that " in 

 crystals and such forms as dolomite and spathic iron we have an 

 adumbration of organic forms." There is a dubiously expressed 

 feeling, even among writers upon evolution, that crystals may to 

 some extent bridge over the great chasm between living and 

 non-living objects. 



Most striking and most surprising of the utterances upon this 

 subject which I have encountered, considering its author, is a 

 remark by fiuxley in an article upon the origin of species, in 

 which he says : — 



' ' The inorganic world certainly has its metamorphoses and, 

 very probably, a long Entwickelungsgeschichte out of a nebular 

 blastema. Who knows how far that amount of likeness among 

 sets of minerals in virtue of which they are now grouped into 

 families and orders, may not be the expression of the common 

 conditions to which that particular patch of nebulous fog which 

 may have been constituted by their atoms, and of which they 

 may be in the strictest sense the descendants, was subjected ? " 



What we are really led to see when we pursue further the 

 comparison between minerals and organisms is not a resemblance, 

 but an irreconcilable difference. 



In the mineral world the forces of nature act upon the 

 individual without producing any modification. 



It is true that by chemical processes a crystal of olivine may 

 have some of its constituents taken from it, and others added to 

 it, whereby it becomes a totally different mineral, serpentine. 

 Or by exposure to the air, a crystal of felspar is converted into 

 crystals of a totally different mineral, china-clay ; but until it is 

 destroyed, there is no change or progress of the individual. Each 

 remains, like Bishop Blougram, "calm and complete, determin- 

 ately fixed, to-day, to-morrow and for ever." There is no 

 response to external stimulus, no adaptation to environment. 



The properties, the form, the beauty of living beings are 

 due to continual interaction between external forces and the 

 organism itself In the organic world the teleological aspect, I 

 imagine, can never be lost from sight ; each in<lividual works 

 for its own salvation ; unceasing change involves either unceasing 

 progress or degradation. With the mineral this is not so. A 

 crystal of natural quartz has doubtless been the same and has 

 possessed the same properties for countless ages. 



In an ever-changing world the crystal is a type of unchanging 

 constancy — its properties remain as permanent as those of the 

 very elements themselves. 



The crystal and the organism differ herein, that in studying 

 the latter we have to take into account not only the unknown 

 properties of the organism itself, but the nature of its environ- 

 ment and the character of the forces to which it is subjected ; 

 whereas in studying the mineral, we find that its properties 



NO. 1392, VOL. 54] 



express only the nature of the crystal in itself, and are therefore 

 the same whatever may be the conditions of its growth and 

 existence. 



When we pass from the crystal even to other inanimate 

 objects, this is no longer the case ; the beauty, the form, the 

 characters of any other natural objects are the result partly of 

 their inherent properties and partly of the forces which act 

 upon them. They have been, to some extent at least, moulded 

 by their environment. The form of a mountain is due partly In 

 the nature of the rock of which it consists, partly to the action 

 of the wind, the water, and the weather to which it is exposed. 

 The curve of a coast-line and the contour of its cliffs are to 

 be attributed partly to the durability or the weakness of the 

 chalk or the slate of which it is composed, but partly also to the 

 sweep of the prevalent currents, the direction of the winds, and 

 the rise and fall of the tide. 



In no character is this more conspicuous than in symmetry 

 of form and character. 



The symmetry of living things is obviously due largely to 

 their environment or to their movement. The symmetry of a 

 tree depends upon the fact that the conditions under which a 

 root grows are different from those which prevail where the 

 branches si)read ; the symmetry of a fish is intimately connected 

 with the fact that it swims in one direction ; the bilateral sym- 

 metry of a man can be, I presume, referreil to a similar cause. 

 There is no inherent symmetry which is absolutely independent 

 of external force. Vary the conditions, and the symmetry of the 

 organism is varied in response. But in the mineral it is other- 

 wise — the symmetry is essential and inherent ; it belongs to the 

 mineral quite independently of external forces. In the study of 

 crystals we are in an altogether unique manner brought face to 

 face with the nature of the thing in itself ; surely an uniquely 

 interesting subject for study. 



But the contrast can be pursued still further. 

 The symmetry of crystals is expressed not only in their 

 external form, but in all their properties internal as well as 

 external. They have been the object of much attention on the 

 part of careful experimentalists using the most refined methods 

 of modern physics, and the result has been to establish this fact 

 in the most unmistakable manner. Their symmetry is one not 

 only of external form, but of internal structure. Further it is 

 of a peculiar character, which entirely differentiates crystals 

 from all other things animate or inanimate. It absolutely dis- 

 tinguishes the crystalline individual from the organism. No 

 crystal has the symmetry of any organism, no organism has the 

 symmetry of any crystal. 



The latter has recently been the subject of much geometrical 

 investigation, which is probably unknown toothers than mineral- 

 ogists, and a very interesting and suggestive discovery has been 

 made by geometers working independently in Germany, France, 

 Russia and England. The physical study of crystals, their 

 action upon heat, light and electricity, has disclosed another 

 remarkable feature characteristic of them. They are without 

 exception homogeneous. At any point within a crystal its pro- 

 perties are absolutely the same as those at any other point within 

 the same individual. This must be due to homogeneity of 

 structure. 



Just as a man walking in an orchard of identical trees planted 

 in a regular geometrical manner, the Roman quincunx for 

 example, would not be able to distinguish one part of the orchard 

 from another by reason of its homogeneity, so we must imagine 

 that Clerk Maxwell's demon, able to transport himself from one 

 point to another within a crystal among the crowd of molecules, 

 or particles, or whatever they may be of which it consists, would 

 not be able to distinguish the one spot from the other. 



The geometricians have therefore inquired in what manner 

 such a homogeneous structure can be symmetrical. 



In other words, if you take an infinite number of identical 

 things, no matter what they be — molecules, portions of matter, 

 systems of forces, or anything else— and range tliem side by side, 

 either parallel to each other, or facing different ways, or turned 

 inside out ; provided only they are so arranged that the distribu- 

 tion at any one part of the mass is the same as at every other 

 part, what will be their symmetry? This is a purely geometrical 

 problem. The solution leads in the most remarkable way to 

 precisely that sort of symmetry which is characteristic of crystals 

 and of nothing else. Hence it follows that the symmetry of 

 crystals results from their homogeneity, and is not an inde- 

 pendent feature. 



The result of our inquiry has been, therefore, not to suggest 



