Friday Evening Proceedifigs at the Royal Institutioiu 817 



ment in the central cavities of the brain and cerebellum, to effect 

 tiie purposes of temporary or permanent adaptation; — That although 

 congenital hydrocephalus may, in the first instance, be referred to 

 certain conditions of the development of the encephalon and its en- 

 velope, these conditions being associated with, or rather expressive 

 of, the special or general plastic powers of the economy, yet the in- 

 ordinate accumulation of fluid in the ventricles of the brain may 

 alio be partly attributed, at a later period, to the faculty of the pia 

 mater before specified, or to any obstruction to the flow of venous 

 blood through the venae Galeni, or the straight sinus; — That the 

 ventricular fluid does not communicate with the sub-arachnoid ca- 

 vity of the spine, as described by M. Majendie, and that the infer- 

 ences which he draws with regard to the movement of the fluid, 

 from the experiments detailed by him, are fallacious, inasmuch as, 

 by interfering with the integrity of the organs containing the cen- 

 tral parts of the nervous system, he thereby removes the most im- 

 portant condition by which the osseous protection is normally cha- 

 racterized, and exposes the parts contained to the direct influence 

 of atmospheric pressure. 



March 13. — Dr. F. Thackeray, V.P., in the chair. Read — Sup- 

 plement to a memoir on the transmission of light in crystallized 

 media, having reference particularly to the laws of biaxal crystals} 

 by Mr. Kelland of Queen's College. Memoir on the laws of fluid 

 motion, by the Rev. S. Earnshaw, of St. John's College. Medical 

 Statistical Report of Addenbrooke's Hospital for the year 1836. 



Mr. Whewell gave an account, illustrated by diagrams, of some 

 of the recent results of his researches on the tides. It was 

 stated that the diurnal inequality, or difference of the two tides 

 on the same day, follows very curious and unexpected laws, which 

 the author has ascertained by means of a series of calculations, 

 executed by Mr. Dessiou and Mr. D. Ross of the Admiralty. 

 This inequality is regulated by the moon's declination, and the ex- 

 actness with which it conforms to a rule, depending on the declina- 

 tion, is very remarkable at some places, as Plymouth and Sincapore. 

 But the declination is followed by the corresponding effect, at inter- 

 vals of time which are different at different places ; the interval 

 being, half a day or a day on the coast of the United States j two 

 days on the coast of Spain and Portugal ; four days at Plymouth ; 

 five at Liverpool ; and apparently twelve days at Leith. Also the 

 amount of this inequality is very great in some cases, for instance, 

 in the Indian Seas. At Sincapore it is so large that one tide is al- 

 most obliterated ; and at other places, as King George's Town, in 

 Australia, this obliteration takes place entirely, and there is only 

 one tide in twenty-four hours at certain periods of the lunation. 



FRIDAY EVENING PROCEEDINGS AT THE ROYAL INSTITUTION 



January 20, 1837. — Mr. Faraday on Mossotti's reference of electri- 

 cal attraction, the attraction of aggregation, and the attraction of gra- 

 vitation to one cause. Signer Mossotti assumes one electric fluid hav- 



