122 



Revieios and Notices of Boohs. 



fixed point, witli a force inversely as the square of the distance, 

 descrihes a conic of which the point is a focus ;" and 



We conclude with the following ingenious application of the 

 law of energy : — 



" When an incompressible liquid escapes from an orifice, the 

 velocity is the same as would he acquired hy falling from the free 

 surface to the level of the orifice. 



For we may neglect (provided the vessel is large compared with 

 the orifice) the kinetic energy (energy of motion) of the bulk of 

 the liquid ; the kinetic energy of the escaping liquid is due to the 

 loss of potential energy of the whole by the depression of the free 

 surface. Thus the proposition at once." 



It is hardly necessary, after these quotations, to make any ob- 

 servation, except to recommend this little pamphlet, as one full 

 of beautiful and ingenious solutions, and as well worthy of being 

 read by all who feel an interest in the subject, but especially by 

 those who mean to study the more complete treatise which the 

 authors have promised to the public. 



Climate : An Inquiry into the Causes of its Dijferences, and 

 into its Influence on Vegetable Life. By C. Daubeny, 

 M.D., F.E.S., &c., Professor of Botany and of Eiiral Eco- 

 nomy in the [Jniversity of Oxford. 



This small volume contains four lectures delivered by Pro- 

 fessor Daubeny before the Natural History Society of Torquay in 

 February last, on Climate and its influence on vegetation. Whilst 

 the subject is handled by the learned professor in its more popular 

 and practical bearings, there is at the same time contained in these 

 able lectures a large amount of valuable scientific information, 

 embodying the recent results arrived at by meteorologists with 

 respect to the atmosphere and its phenomena. In the discus- 

 sion of the question, the author defines the climate of a country 

 to be its relations to temperature, light, moisture, winds, atmo- 

 spheric pressure, and electricity ; but amongst these the first place 

 must be conceded to the intensity of the heat, and to its distribu- 

 tion over different portions of the year, as it is this which in a 

 great degree regulates the other conditions, and is also itself of all 

 others the one most indispensable for the exercise of the functions 

 of vegetable and animal life. This important element of heat is 

 derived from the living bodies scattered over the globe, from the 

 various processes carried on by natural agencies or through the 

 instrumentality of man, from the interior of the earth, and from 



