VOL. XXXIII.] PHILOSOPHICAL TRANSACTIONS. QQ 



her breathing as difficult as ever; so that he now thought all his labour had 

 been in vain ; yet he opened it again with a larger orifice, and from that time 

 dressed it successfully to the perfect healing. The menses returned, and the 

 patient continued after in a good state of health. 



^n Experiment to illustrate what luas said in N° 386, 387, 388,* concerning 

 the Figure of the Earth. By the Rev. J. T. DesaguUers, L. L. D. F. R. S. 

 N° 389, P- 344. 



On an axis of iron made to turn swiftly, by means of a wheel, whose string 

 went round a pulley fixed to the said axis, Dr. D. slipped on two iron hoops, 

 whose planes intersected at right angles, representing two colures, which, being 

 of a spring temjjer, sprung in such manner as to be -^ part longer in that dia- 

 meter that coincided with the axis, than in their equatorial diameter; this pro- 

 portion being the same that Mr. Cassini supposes to be between the axis and 

 equatorial diameter of the earth. Two circular plates, to which the said hoops 

 were rivetted, had square holes, through which the axis passed, so that the two 

 poles of the oblong spheroid, which the hoops describe in their revolution, 

 might approach together in such manner, as to let them put on the form of a 

 true sphere, when, oy the whirling, the equatorial diameter of the machine 

 swelled and overpowered the elasticity of the hoops. A greater degree of swift- 

 ness turned the sphere into an oblate spheroid of Sir Isaac Newton's figure. 

 A velocity still greater makes the disproportion of the diameters, such as 

 those of Jupiter; and still the equatorial diameter increases with the centrifugal 

 force. 



Another hoop with a catch, representing the equator, shows the increase of 

 the equatorial circumference; and an index, applied to the frame, shows the 

 increase of the diameter. 



As soon as the revolution of the machine ceases, the colures, meridians or 

 hoops return to their elliptical figure, whose longest diameter is the axis of 

 revolution. 



If the force, by which the hoops endeavour to keep their figure, be consi- 

 dered as the gravity that keeps together the parts of the earth; from this 

 experiment, compared with what has been said in the translations abovemen- 

 tioned, it will appear that the earth cannot preserve its figure, unless it be an 

 oblate spheroid. 



* An abstract of all the papers will be found at p. 6], of this voL 

 o 2 



