243 



at Liverpool, under the direction of Captain Denham, R.N.; and 

 twelve months' observations made at Bristol, by Mr. Bunt, by means 

 of his tide-gauge. According to the theory of the tides, the height 

 of the surface of the water at a given place will increase as the sine, 

 while the time increases as the arc. Hence if the time be made the 

 abscissa, and the height the ordinate, the curve representing one 

 tide would be the Jigure of signs. The author on making the com- 

 parison of the empirical curve of the rise and fall of the water, de- 

 duced from observation, with this theoretical curve, finds a general 

 agreement betw^een them ; subject to certain deviations, consisting 

 principally in the empirical curve indicating that both the rise and 

 the fall are not symmetrical, like the theoretical curve, in conse- 

 quence of the fall being generally more rapid than the rise, and thus 

 occasioning a displacement of the summit of the curve towards that 

 branch of it which corresponds to the fall. 



9. Researches in Embryology. Third Series. — Additional Ob- 

 servations. By Martin Barry, M.D., F.R.S. 



Having in the paper to which the present is supplementary made 

 known the fact that the germinal spot in the mammiferous ovum re- 

 solves itself into ceils, with which the germinal vesicle becomes filled, 

 the author has since directed his attention to the corresponding parts 

 in the ova of birds, batrachian reptiles, and osseous fishes, which he 

 finds to be the seat of precisely the same changes. The numerous 

 spots in the germinal vesicle of batrachian reptiles and osseous fishes 

 are no other than the nuclei of cells. The cells themselves, from 

 their transparency, are at first not easily discerned, and appear to 

 have hitherto escaped notice; but after the observer has become 

 aware of their presence, they are, in many instances, seen to be ar- 

 ranged in the same manner, and to present the same interior them- 

 selves as the corresponding cells in the ovum of mammalia. 



In the representations given by Professor Rudolph Wagner, the 

 discoverer of the germinal spot, the author recognizes evidence of 

 the same changes in ova throughout the animal kingdom. He con- 

 firms and explains the obser\^ations of R. Wagner, that in the ova 

 of certain animals an originally single spot divides into many, and 

 that in the ova of other animals the number of spots increases as 

 the ovum ripens. But he expresses also the opinion that in all ova 

 there is originally but a single spot, this being the nucleus of the 

 germinal vesicle or cell. 



The analogy between the ova of mammalia and the animal above- 

 mentioned, extends also to the substance surrounding the germinal 

 vesicle, which consists of nucleated cells. 



10. Description of a Calculating Machine invented by Mr. Thomas 

 Fowler, of Torrington in Devonshire. By Augustus De Morgan, Esq. 

 Communicated by F. Baily, Esq., V.P.R.S. 



The arithmetical operations performed by the machine are those 

 of multiplication and division ; the factors and product in the for- 

 mer case, and the quotient, dividend and divisor in the latter, being 



