Dr Rose on Zinkeniie, a New Mineral Species. 17 



changing in age to that of the male. Mr John Hunter had 

 previously noticed this change in the hen-pheasant and pea-hen, 

 in a Memoir published in the Philosophical Transactions, also 

 unnoticed by M. Saint-Hilaire ; and Mr Butter has collected 

 a number of instances, not only among the Gallince, but also 

 among the Palmipedes and Waders, of similar changes. A 

 figure of the common domestic hen in the plumage of the 

 male, illustrates Mr Butter's paper ; and the circumstance of 

 the female of this species when aged, essaying to crow like the 

 cock, is a fact known in every poultry-yard in this country. 

 A vulgar prejudice permits not the change in plumage to be 

 carried further ; for a crowing- hen being accounted unlucky, 

 the death of the animal always follows this incipient change. 

 A specimen of a pea-hen beginning to assume the male plu- 

 mage, is, we believe, in the Museum of the University of 

 Edinburgh. Mr John Hunter regards this change in the 

 female plumage as monstrous ; but Mr Butter, with more ap- 

 pearance of truth, is disposed to consider " that this change 

 of plumage in old hens, is not confined to one, two, or three 

 different species, but that probably the same disposition is 

 common to numbers of the feathered race ;" — " and that the 

 change is almost always natural, produced either by the effects 

 of age, of sterility, or other causes which tend to work some 

 changes in the constitution of birds." 



Art IV. — On Zinkenite, a New Mineral Species. By Dr 

 Gustavus Rose. Communicated by the Author. 



Ihe shape of the crystals of Zinkenite most nearly resembles 

 Plate I. Fig. 3, which is a regular six-sided prism (M,) termi- 

 nated by obtuse six-sided pyramids, (P,) whose faces are set 

 on the edges of the prism. 



The following are the principal measures of the angles, cal- 

 culated from the admeasurement given = 150° 36', upon the 

 supposition of the prism being a regular one. 



if on M = 120° 0'. 



P on M - 102° m. 



P on P (adjacent) = 165° 2G f . 



P on P (over the apex) — 150° W. 



VOL. VI. NO. I. JAN. ]827. B 



