PREFACE. Several of the works I 'have now mentioned were publifhed when the Wernerian ory&ognofie was far removed from its prefent ftate of perfection, and are confequently in many refpefts imperfect. The mine- ralogy of the intelligent M. Brochant, which may be confidered the belt account of the Wernerian oryCtog-* noftic fyltem hitherto publifhed, is unfadsfaCtory. In the work 1 am now to lay before the public, I fhall, in the two firft volumes, deliver a fyftem of bryctognofie, in which I (hall follow the arrangement and method of delcription of W erner, and when I "Venture to deviate from the fyftem of my illuftrlous tnafter, I hope to be able to aflign fatisfa&ory reafons for the alterations I may propole *. r lhe taik which I have undertaken was to have keen executed by my ever to be regretted friend, Dr Uciell, whofe long experience and confummate 11 eminently qualified him for it. Unfortunately p r are arranged together; and 3d,' Of columnar heavy fpar we have the following delcription : “ Ufually of bright white colour. |( P carI y* Either tranflucent or tranflucent on the edges. - 1 > and its cry Hals are aggregated ittto columns.” This is er Hi iking inilance of the infufficiency of all methods that ch i A em ^ raCe * n accou nt of the fpecies all its external * S trS> an< ^ ^ arraI1 S £mcnt the natural alliances, the c ^ ^ le names an( I ex preffions which will occur during . e ,°^ ^' 8 v °lume, and which may by fome he difficultly un er 00 , will be fully explained in the treatife on the External - s, which will accompany the fecond volume, and in the ume on reognofie. I trull therefore that the language which I have employed will not be criticifed with fevcrity, until I have an opportunity of explaining it.