58 i Analyses of Books. [J as. 



maximum temperature of the sea is about three, p.m. and the 

 minimum towards sun-rise. One of the most considerable of 

 the causes that disturb the temperature of the ocean is currents, 

 and these currents affect it in different ways, according to the 

 cause which produces them. Superficial currents often depend 

 upon prevailing winds, and these currents are then warmer or 

 colder than the other parts of the sea, according to the quarter 

 from which the wind blows. Currents often depend upon in- 

 equalities in the bottom of the ocean ; and it is now admitted as 

 a fact, established by many observations, that when the sea is 

 shallow its temperature its diminished. The author gives us the 

 result of his observations on the currents which he encountered 

 during his voyage, which all accord with the general principles 

 stated above. He gives us the particular account of the effect 

 produced by the well-known current flowing from the south-east 

 coast of Africa. In crossing this current the temperature of the 

 ocean suddenly varied as much as 10 degrees, which is probably 

 occasioned by a sudden transition from the water which lies over 

 the bank of Lagullas, along which the current rapidly flows, 

 into the stream itself. 



A certain conjunction of circumstances, connected with the 

 warm streams of water, and cold winds blowing over them, is 

 employed by our author to explain a phenomenon which has 

 been often described by travellers who have visited the Cape, 

 commonly called the " Table-cloth." It consists in a cloud or 

 mist, which covers the upper part of the Table Mountain, but 

 which does not descend to the plain below. The phenomenon 

 only occurs when the south-east wind blows, which is there a 

 cold wind, and, passing over the warm currents in its way to the 

 land, condenses a portion of aqueous vapour, and produces a- 

 mist, which is carried along the eastern side of the mountain, 

 and covers the top, but does not descend on the western side, 

 in consequence of the heat of the plain below, but is suspended 

 over it, in the form of a sheet, whence it has derived its name. 



(To be continued.) 



Traitt de Physique experimentale et Mathematique, par J. B, 

 Biot, Membre de I'Academie des Sciences, $£. fyc. 4 torn. 8vo. 



In the history of the proceedings of the Royal Academy of 

 Sciences, which appeared in our last volume, some account was 

 given of this treatise ; but as it is a work which, both from its 

 own merits, and from the celebrity of the author, must excite 

 considerable interest with our readers, we conceive that a some- 

 what more detailed analysis of it will not be unacceptable to 

 them. It will indeed be impossible, in the limits of a few pages, 

 to enter into an examination of the manner in which M. Biot 

 treats the various topics that pass under his review, or to pro- 

 nounce upon the merits of the reasoning which he employs in 



