Dr Brewster on the Structure, #c. of Haytorite. 301 



Mr Levy concludes his observations in the following words : 

 " There is not, therefore, sufficient evidence, perhaps, to say- 

 that the crystals of Haytorite are pseudomorphic of Humbold- 

 tite. The repositories of the two substances seem to be dif- 

 ferent ; for, besides the already known localities of Humbold- 

 tite, the Seisser Alp in the Tyrol, and Salisbury Craigs, near 

 Edinburgh, I know only of another, which is Utoe in Sweden, 

 where, to judge by the specimen in Mr Heuland's collection, 

 it occurs in macled crystals, and accompanied by apophyllite, 

 carbonate of lime, sulphate of barytes, and bitumen. 



ie In conclusion, it may be said, that if the reasons for sup- 

 posing the crystals of Haytorite appear conclusive, there is 

 some not unreasonable ground to think they may owe their 

 form to Humboldtite, but have been modelled upon crystals of 

 that substance, larger, and of a different variety than those 

 which have been met with hitherto, or otherwise they must be 

 considered as pseudomorphic crystals of an unknown species." 



Art. XXX. — Observations on the Structure and Crystalline 

 Forms of Haytorite. In a letter from Dr Brewster to 

 Cornelius Tripe, Esq. Devonport. 



Sir, 

 As you were so kind as to send me specimens of the new mine- 

 ral recently found in Devonshire, to which you have given the 

 suitable name of Haytorite, I need not make any apology for 

 addressing to you the results of the observations which 1 have 

 thus been enabled to make upon its structure and crystalline 

 forms. 



It was impossible to peruse the ingenious observations of Mr 

 Phillips and Mr Levy without being impressed with the opi- 



