413 



In the course of these experiments Dr. Wells observes, that the 

 sympathy between the eyes, which is in general considered as sym- 

 pathy of the iris, is in fact sympathy of the retina ; for when the 

 pupil of one eye is dilated by belladonna, the pupil of the other be- 

 comes so much the more contracted, in consequence of the greater 

 light which the enlarged pupil admits. 



He remarks, also, that though he has lost, in great measure, the 

 power of adaptation, he has in no degree lost any command of the 

 external muscles, but can make the optic axes meet at any short 

 distance from his face, to which he could formerly make them con- 

 verge. So also, while Dr. Cutting's eyes were under the influence 

 of belladonna, the powers of the external muscles remained unim- 

 paired ; whence it appears, that the power of adapting the eye to 

 different distances is not dependent on the external muscles, but 

 rather to be referred to the crystalline lens, although the muscularity 

 of that organ does not appear to Dr. Wells to be by any means 

 established. 



On the Grounds of the Method which Laplace has given in the second 

 Chapter of the third Book of his Mecanique Celeste for computing 

 the Attractions of Spheroids of every Description. By James Ivory, 

 A.M. Communicated by Henry Brougham, Esq. F.R.S. Read 

 July 4, 1 81 1 . [Phil. Trans. 1 81 2, p. 1 .] 



Sir Isaac Newton, who first considered the figure of the earth and 

 planets, confined his view to the supposition of their having been 

 originally in a fluid state ; and he conceived them to retain the same 

 figure which they assumed in their primitive condition ; and those 

 mathematicians who succeeded him in the same path of inquiry have 

 seldom ventured beyond this limited hypothesis, and have shown, 

 that when a body composed of one uniform fluid revolves about its 

 axis, or even if it consists of several fluids of different densities, its 

 parts will be in equilibrium, and it will preserve its figure when it 

 has the form of an elliptic spheroid of revolution oblate at the poles. 



But though the supposition of original fluidity of the mass simpli- 

 fies the investigation, it does not seem to be warranted by what we 

 see of the surface ; for in that case, Mr. Ivory observes, the arrange- 

 ment of all the heterogeneous matters would have been according to 

 their densities ; those least dense occupying the surface with gradual 

 increase of density to the centre ; whereas, on the contrary, nothing 

 can be more irregular than the density of such solid parts of the 

 earth as come under our observation, and the elevation of continents 

 above the level of the sea, as well as the depths of the different 

 channels which contain the waters of the ocean. 



Moreover, according to the latest and best observations made for 

 the express purpose of determining the figure of the earth, it jdoes 

 not appear to be of any regular elliptic form. 



Since the hypothesis of Newton is, therefore, not consonant to 

 observation, it became necessary to consider the subject in a more 



