93 



in tin luminous source from which the polarised light 

 its origin. 



I '.ut the whole complex of li^ht-phenomena (radiations) in tin 

 tin r, or in a crystal of calcite, etc., caused by this luminous SOUP e, 

 tainlv tin- same symmetry (K) as that of the ether, or a 

 (> ^vmmetry (/>) than that of the ca/a ^-crystal. *) 



in this and analogous examples we can in general conclude 

 it a lack of symmetry-properties in the causes of physical pheno- 

 , can, (and in by far the greater number of cases will really) be 

 iani U-sted also as a lack of symmetry-properties of the effects 

 >roduced, but that this need not be always the case. From the ab- 

 mv of symmetry-properties in the effects observed however, 

 is certainly necessary to conclude, that there is a similar lack 

 )f symmetry-properties in the producing agents. 



In other words: the effects may have occasionally the same or a 

 igher symmetry than the producing causes, but the last cannot have 

 higher symmetry than the effects observed. 



It is moreover worth remarking in this connection that symmetry- 

 )roperties which are present in all causes, and in all circumstances 

 governing a certain phenomenon, are necessarily always found in 

 ic effects produced also. However we must always be sure that 

 ic number of causes considered is really complete; evidently it is 

 many cases hardly possible to get full assurance of this. 

 11. After the general remarks on the dependence of the sym- 

 letry-character of causes and effects in physical phenomena, we 

 ?turn to the consideration of some special symmetry-properties 

 >t <vrtain physical states and to the question, in what way several 

 simultaneously acting causes can cooperate as a resulting cause, 

 producing certain effects. 2 ) 



If a crystal of calcite is traversed by rectilinear polarised light, 

 md if we wish to give an exhaustive description of the way in which 

 ic propagation of light-waves takes place therein, experience 

 teaches us that it is sufficient for this purpose, if we adopt as the 

 'image" of the phenomenon in every point P a rotation-ellipsoid 



>) The "image" f of the phenomenon of the propagation of rectilinear 

 polarised light in a calcite-crysta.}, can be reprensentetl by a rotation-ellipsoid 

 in every point P, with its axis of isotropy parallel to the trigonal axis of 

 this clitrigonal crystal. (See below). 



2) Cf. P. Curie, Journal de Physique. (3). 3. 407. (1894); Bull, de la Soc. 

 Min. 7. 89, 418. (1884). 



