318 



He then observes, that it is no uncommon thing to find, among 

 numerous broods of pheasants reared by hand, some females, which, 

 at the age of only four months, produce the brightest plumage of the 

 male ; and in two instances of birds shot in a wild state, the nest 

 feathers had not been shed, proving them to have been birds of the 

 year. 



A partridge, having a white bar across the breast, and the first 

 three primary feathers in each wing white, being opened, exhibited 

 the same sort of organic disease ; and from circumstances adduced, 

 it appears that this was also a bird of the year. 



All variations in plumage, however, are not traceable to this cause. 

 In most of the excepted instances, however, the individuals are dwarf 

 birds, and the author attributes their variety of plumage to defective 

 secretion, the effect of weakness. 



When the sexual organs are artificially obliterated in the common 

 fowl; in the male bird, so soon as this operation is performed, he 

 ceases to crow ; the comb and gills do not attain their full size ; the 

 spurs remain short and blunt ; and the feathers of the neck assume 

 an appearance intermediate between the hackled appearance of the 

 cock, and the ordinary web of the hen. The operation on the female 

 being performed (by obliterating the oviduct), the ova cease to en- 

 large ; she makes an imperfect attempt to crow ; the comb increases 

 in size ; and short and blunt spurs make their appearance. The plu- 

 mage also alters both in colour and form, and approaches that of the 

 cock ; and the bones of the lower part of the back never acquire that 

 enlargement requisite for giving a proper breadth to the pelvis. In 

 short, the two sexes by this process approximate so nearly in charac- 

 ter, that it is frequently difficult to determine the sex. 



In the case of hen-pheasants, they assume the plumage of the male 

 at best but imperfectly, and it is probable that they do not live many 

 years after the change. 



The author concludes by regarding it as a general law, that where 

 the sexes of animals are indicated by external characters, these un- 

 dergo a change, and assume a neutral appearance whenever original 

 malformation, subsequent disease, or artificial obliteration, has de- 

 prived these organs of their true influence. 



On the secondary Deflections produced in a Magnetized Needle by an 

 Iron Shell, in consequence of an unequal Distribution of Magnetism 

 in its two Branches. First noticed by Captain J. P. Wilson, of the 

 Honourable East India Company's Ship Hythe. By Peter Barlow, 

 Esq. F.R.S. Mem. Imp. Sc. Petrop. Read May 17, 1827. [Phil. 

 Trans. 1827,^.276.] 



Captain Wilson being engaged in the prosecution of Mr. Barlow's 

 inquiries as to the laws of the deflection of a needle by an iron shell, 

 had remarked, while in China, that when a magnetic needle was 

 placed in the equator of an iron shell, though no deviation arose 

 when the compass was in its natural state, yet when one end of the 



