Introduction. it 



always found the utmost facility afforded to research 

 by the habitual urbanity and friendly attention of Mr. 

 Konig. And I have frequently been indebted also te 

 Mr. G. B. Sowerby for illustrative specimens of mine- 

 rals of unfrequent occurrence. 



Since the committal of a considerable portion of 

 these pages to the hands of the compositor, and in- 

 deed subsequently to the printing a large part t>f the 

 volume, a new edition has appeared of the Abbe 

 Hairy 's treatise on crystallography; this event was 

 very soon followed by the decease of the learned 

 author; and subsequently to his decease three vo- 

 lumes of a new edition of his treatise on mineralogy 

 have been published : events so intimately connected 

 with the subject of this volume that I cannot well 



.,!_ T 



pass them over in silence. 



I am perfectly disposed to concur in the public 

 eulogium which has been so deservedly passed upon 

 the deceased philosopher, for having been the first 

 to elevate crystallography to the rank of a science, 

 and to trace out a secure path to its attainment; but 

 I regret that I cannot agree in that unqualified ap- 

 probation of his recent works which some of his sur- 

 viving friends have so liberally bestowed upon them. 

 For those works will be found to contain errors of so 

 remarkable a character, as to excite our surprise 

 when we recollect the generally accurate and enlight- 

 ened judgment of the author. 



Upon these, as criticism can no longer reach the ear 

 of the author, I shall offer but few remarks. 



One of his sources of error may be discovered in an 

 apparently groundless notion which his theory em- 

 braces, that nature has imposed limits to the angles 



