Bcuncc IPragrcss, 



JVew Series. No. 2. January, 1897. Vol. I. 



LIQUID CRYSTALS. 



THE very name seems to be a self-contradiction. How 

 can a liquid be a crystal, and how can a crystal be a 

 liquid ? 



The term was introduced by Dr. Lehmann, of Karls- 

 ruhe, and relates to certain remarkable bodies which, if we 

 accept his interpretation, must entirely revolutionise current 

 views regarding the structure of solids and liquids. 



In previous articles I have attempted to explain the 

 newer theories of crystal structure, and have suggested that 

 in their geometrical aspect they harmonise in a most satis- 

 factory manner with observed facts. Now the very essence 

 of these theories consists in the solidity of the crystal struc- 

 ture ; it all the more behoves me, therefore, to call attention 

 to the work of an investigator who regards these theories as 

 of no essential importance and would deprive them of the 

 basis on which they have been erected. 



The observations of Lehmann are so curious and sur- 

 prising that, whether his interpretation of the facts be cor- 

 rect or no, both the facts and the interpretation deserve 

 serious attention. Although nearly six years have passed 

 since the publication of his papers on the subject, litde 

 more than brief mention of them, so far as I am aware, has 

 appeared in English ; they have not been repeated either 

 to be verified or invalidated ; authors who have referred to 

 them have been careful to quote the observer's own words, 

 without either accepting or rejecting his conclusions ; or, if 

 they have expressed any criticism, have done so in an 



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