Folyadelphite, 65 



Oxygen. Ratio. 



Alumina, 30-49 14-24 1 ^^.^ o o 



Peroxide of iron, 30-00 9-19 / -^"^ *'^ ^ 



Protoxide of iron, 11-93 2-72 



Protoxide of manganese, 7*60 1-70 J. 7*76 



Oxide of zinc, 16-80 3 



-721 



-70 I 

 •34 J 



Here it is evident that the atoms of acid and bases are to each other 

 as three to one, which is the case, also, with Automalite, taking Abich's 

 analysis, and grouping the isomorphous bases, thus : 



Dr Thomson, the only chemist who has analysed Dysluite, reckons 

 all the iron as peroxide, and as the principal basic constituent of the 

 mineral, which, in his view, consists of the aluminates of iron, zinc, 

 and manganese. E-ammelsberg, in stating the analysis, has given 

 both oxides ; and the atoms of alumina and peroxide of iron, as put 

 down by him, are 22'80, and those of the isomorphous bases — pro- 

 toxide of iron, protoxide of manganese, and oxide of zinc — are 7*83 

 (7.89 V) ; thus giving the same ratio as that above stated. 



But other reasons may be urged why Dysluite should be regarded 

 only as a variety of Automalite. I have seen specimens on which 

 there were crystals well claiming the name of Dysluite, as well as 

 others equally entitled to the name of Automalite ; while there were 

 yet others, evidently passing from one into the other, — the bright 

 and perfect crystals of Automalite gradually losing their lustre, be- 

 coming porous, comparatively brittle and soft. I think if these cir- 

 cumstances had been attended to in the early history of the mineral, 

 the name Dysluite would long since have departed from the catalogue 

 of mineral species. 



PolyadelpJdte. — As Dana, in the new edition of his Mineralogy, has 

 very properly included this mineral under the species garnet, I merely 

 refer to it, to give further evidence of the correctness of his opinion, 

 from circumstances connected with its occurrence at the locality. It 

 is evidently a granular, imperfectly crystallized yellow garnet, and 

 the specimen which I received, ten years ago, from Professor Nuttall, 

 contains mechanical mixtures which it would be impossible to sepa- 

 rate from it, so as to give us entire confidence in its analysis. To 

 these, I believe, we may attribute its departure in composition from 

 the common brown or yellow garnet, though it does not differ much 

 from the brown garnet of Franklin, analysed both by Dr Thomson 

 and Mr Seybert. 



VOL. XLII. XO. LXXXIII. — JANUARY 1847. B 



