British Association. 307 



paring the changes which take place in the polarizing structure 

 of the crystalline lenses of animals in old age, with those after 

 death, the lenses being placed in distilled water, as being the 

 only fluid which did not affect their transj)arency. From these 

 investigations Sir D. Brewster has been led to conclude that there 

 is in the crystalline lens a capability of being developed by the 

 absorption of the aqueous humour ; that a perfect structure is not 

 produced until the animal frame is completely formed, and that, 

 when it begins to decay, the lens changes its density and focal 

 length, and sometimes degenerates into that state called hard and 

 soft cataract. Sir D. Brewster is led to entertain a hope that these 

 researches may furnish a means of preventing or curing this alarming 

 disease. 



4. The Rev. Mr. M^Gauley having been called on by the 

 President to read a paper in continuation of the one which he gave 

 last year, respecting the theory of the Application of Electro- 

 Magnetism to Mechanical Purposes, began by stating that he 

 had met with many practical difficulties, as might be expected, in 

 preparing for the Section a small model of a machine, intended to 

 act with effective power ; one of the most serious of these was, that 

 the crank and fly-wheel could not be made to move along with the 

 primary moving pendulum. He then proceeded to give his views 

 of the theory of electro-magnetic influence, and the best modes of 

 constructing the several parts of the apparatus, so as to produce the 

 greatest effect, and illustrated the whole by copious extracts from a 

 most laborious course of experiments. 



WednesdaT/, 24th Avgust. — 1. The business was commenced by 

 3Ir. Harris, " On some Phenomena of Electrical Kepulsion." The 

 author endeavoured to show in this paper that, from the disturbing 

 force of electrical induction, the indications of electricity, operating 

 by repulsion, are often anomalous and irregular, and do not, under 

 all circumstances, indicate the quantity of electricity with which the 

 repelling bodies, either one or both of them, are charged ; he deter- 

 mined the nature of the cases in which the disturbing influences of 

 induction may be supposed to arise. The author further gave the 

 results of some inquiries on the nature of the tangent disc, and 

 was led to believe that it may be greatly influenced by position on 

 the charged body ; intensity of the charge, thickness, or other exten- 

 sion, and the like, without any reference to electrical distribution on 

 the body touched. The author conceived that the present theories 

 did not account for the phenomena of electricity satisfactorily, and 

 that we may eventually find electrical action reducible to a system 

 of undulations set up in the finely attenuated medium between the 

 surface of bodies. 



2. Professor Challis' Supplementary Report on the Mathe- 

 matical Theory of Fluids. — This report gives an account of the 

 application of mathematics to problems in the equilibrium and 

 motion of fluids, which had not been touched upon in the author's 

 previous reports. These were principally the mathematical theory 

 of clastic fluids, as bearing on the determination of the heights of 

 mountains, and the barometer, and the amount of astronomical 



X 2 



