Drs. Tiedemann and Gmelin in reply to Dr. Prout. 3 



earliest mineralogical friends, the acknowledgement of the 

 many instances of his having communicated to me rare speci- 

 mens for examination, particularly during my stay at Freiberg. 

 2. Herderite occurs imbedded in fluor, in the tin mines 

 of Ehrenfriedersdorf; in Saxony. It resembles apatite, with 

 which it was formerly confounded, in a remarkable degree ; 

 particularly some of those named asparagus-stone : such as the 

 variety from Zillerthal, in Salzburg, and that from Hof in 

 Gastein in the same country, which is found accompanying 

 the axotomous iron-ore of Mohs, and still more so certain 

 pale greenish- white masses of the same species, which occur, 

 though in small quantity, along with the zoisite from the 

 Saualpe in Carinthia. The resemblance among those species 

 is sufficient to class the herderite in the genus Fluor-haloide of 

 Mohs, in which it may be henceforth included as the "pris- 

 mati Fluor-haloide" 



II. Reply of Drs. Tiedemann and Gmelin to the Remarks of 



Dr. Prout inserted in the Annals of Philosophy (Second Series), 



vol. xii. p. 405 : Communicated by Thomas Thomson, M.D. 



F.R.S. fyc. Regius Professor of Chemistry in the University 



of Glasgow. 

 r T > HE more satisfied we are of the obligations which the 

 * doctrine of digestion lies under to Dr. Prout, and the less 

 intention we had to attack him unjustly, the more do we con- 

 sider it as our duty to discuss the complaints which he has 

 made, so far as we are concerned, — to defend ourselves, where 

 we think ourselves in the right, and to acknowledge our mis- 

 takes where we think ourselves in the wrong. 



Dr. Prout's complaints are the following : 



1 . We have led our readers to believe that Dr. Prout denies 

 the presence of every other free acid in the contents of the sto- 

 mach, except the muriatic; which is not the case. 



Yet we could draw no other conclusion from Prout's paper*, 

 than that he denied the presence of every other acid. For 



a. He says (page 118), " the experiments above mentioned 

 seemed to preclude the possibility of the presence of any de- 

 structible acid ; and the only known fixed acids likely to be 

 present were the sulphuric and phosphoric; the muriate of 

 barytes, however, neither alone nor with the addition of am- 

 monia, produced any immediate precipitate, showing the ab- 

 sence of these two acids in any sensible quantity, and still 

 further confirming the results as before obtained." 



b. Now unless the absence of other free acids be taken for 



* Phillips's Annals of Philosophy, vol. viii. p. 117. 



B 2 granted, 



