10 Mr. Tredgold on the Flexure 



much larger and wider. There was not any appearance of 

 impregnation in the right ovarimn.' I cut out the whole of 

 the internal parts of generation, the urinary bladder, part of 

 the rectum, and also the whole of the cloaca unexamined, and 

 put them into spirits. This preparation is now in the posses- 

 sion of Mr. Scott, who is to take it w ith him to England, and 

 who will, I am sure, feel much pleasure in showing it to you*. 

 In this preparation the urinary bladder must not be mistaken 

 for an uterus. 



" Cookoogong a native, chief of the Boorah Boorah tribe, 

 says, that it is a fact well known to them, that this animal lays 

 two eggs, about the size, shape, and colour of those of a hen ; 

 that the female sits a considerable time on her eggs, in a nest 

 which is always found among the reeds on the surface of the 

 water ; that the animal can run on the grass, and is sometimes 

 found at a considerable distance from the water ; that he is 

 also perfectly aware that a wound from the spur of the male 

 is followed by swelling and great pain; but although he has 

 seen many cases of it, he has never known it fatal ; that the 

 flesh of the animal is never eaten, and that the native name is 

 MuUi7is:ons..^' 



V. Observations on the Flexure of Astronomical Instrumeiits. 

 By Mr. Thomas Tredgold, Civil Engijieer. 



[Continued from vol. Ix. p. 340.] 



On the Derangement of Circles. 



T F the plane of a circle be graduated in a horizontal position, 

 -*■ and it be intended to be used in a vertical one, let us con- 

 sider the nature, and endeavour to estimate the extent of the 

 derangement, such a change of position may be expected to 

 produce. 



In the first instance, let the circle be a plane, of uniform 

 thickness, supported upon a horizontal axis ; and suppose this 

 circle to be represented by A B C D, Plate I. fig., where E is 

 the axis, and Gg the centre of gravity of the semi-circles ADB, 

 andACB. 



Respecting the nature of the derangement in this case, it is 

 evident that the weight of the semi-circle ADB must tend to 

 depress the point D, and the weight of the opposite one equally 

 to depress the point C. And also, that by their joint action 

 the upper part of the circle will be extended, and the lower 



* Mr. Scott, on his arrival in England, presented the preparation to the 

 University of Oxford. 



part 



