NATURAL HISTORY OF SELBORNE. 89 



feathers growing not from their uropy(/ium, but all up 

 their backs. A range of short, brown, stiff feathers, about 

 six inches long, fixed in the uropygium, is the real tail, and 

 serves as the fulcrum to prop the train, which is long and 

 top-heavy when set on end. When the train is up, nothing 

 appears of the bird before but its head and neck ; but this 

 would not be the case were those long feathers fixed only 

 in the rump, as may be seen by the turkey-cock when in a 

 strutting attitude. By a strong muscular vibration these 

 birds can make the shafts of their long feathers clatter like 

 the swords of a sword-dancer ; they then trample very 

 quick with their feet, and run backwards towards the 

 females. 



I should tell you that I have got an uncommon Calculus 

 cegogropila, taken out of the stomach of a fat ox ; it is 

 perfectly round, and about the size of a large Seville 

 orange ; such are, I think, usually flat. 



LETTER XXXVL 



Sept. 1771. 

 The summer through I have seen but two of that large 

 species of bat which I call Vespertilio altivolans, from its 

 manner of feeding high- in the air : I procured one of them, 

 and found it to be a male ; and made no doubt, as they 

 accompanied together, that the other was a female ; but 

 happening in an evening or two to procure the other like- 

 wise, I was somewhat disappointed when it appeared to be 

 also of the same sex. This circumstance, and the great 



