Shepard^s Treatise on Mineralogy. 177 



it under Gigantolite ! Mr. Augustus A. Hayes, in his reexamina- 

 tion of microlite and pyrochlore, (Vol. xlvi, p. 158,) says that "as 

 Mr. Teschemacher (his colleague in the controversy) has seen 

 nothing in the reply of Prof. S. leading him to doubt the correct- 

 ness of his statements, he declined noticing the article," while 

 for himself, he shall still adhere to the chemical part of the dis- 

 cussion, and " leave those rules which separate the microlite from 

 pyrochlore, and place it with yttro-tantalite, their full injEiuence." 

 He farther adds, that the absence of yttria, (whose presence was 

 claimed by my research,) is proved by repeating my own experi- 

 ments, and further observes that my own results do not favor the 

 conclusion I adopted. Fortunately for myself in this delicate con- 

 juncture, where I am not allowed to interpret my own experi- 

 ments, I have it in my power to bring the opinion of a third per- 

 son, to whom in a chemical dispute I suppose my antagonist will 

 at least be willing to defer. In his annual report on the progress 

 of chemistry for 1842, Berzelius observes, "In the report for 1835, 

 p. 208, there was a notice of a mineral, found in small quantity 

 with the tantalite of Chesterfield, in North America, and to 

 which the name of microlite was given. This mineral has been 

 made the subject of two researches, (Silliman's American Jour- 

 nal, Yol. xLiv, pp. 33 et 116,) which do not give, as would appear, 

 an exact analysis of it, though they seem to prove that it is no- 

 thing more than a yellow yttro-tantalite." 



Mr. Teschemacher has, however, so far altered his mind as to 

 come out again with the following notice, which he has publish- 

 ed in this country and in England.* " The close examination of 

 above two hundred crystals, of the mineral named microlite by 

 Prof. Shepard, and the comparison of them with about fifty crys- 

 tals of pyrochlore from the Swedish localities, and from the Ural 

 Mountains, resulting in their agreement in color, cleavage, crys- 

 talline form and modifications, indicated to me in 1841 the com- 

 plete identity of the two minerals, although Wohler's analysis 

 had decreed the latter to be a titanate, while Shepard's had made 

 the former a columbate of lime. 



" This identity, strenuously resisted by Prof. Shepard- although 

 on grounds which show a very superficial knowledge of the 

 whole subject, has been completely proved by subsequent analy- 

 ses, particularly by that of A. A. Hayes in Silliman's Journal, 



* Boston Jour. Nat. Hist., Vol. IV, p. 50, and Lond. Ed. and Dub. Phil. Mag. 

 Vol. xLviii, No. 1.— Oct.-Dec. 1844. 23 



