Reviews, ^-c— " The Botanist." 371 



or, which is the same thing, 



^ = p4^, (3.) 



as the general equation of the conic sections. 



For since the force in the radius vector varies as -5-, its 



1 P 



component in the direction of the normal must vary as -^j- . -— . 



But the normal force is 



v" C P^ 



K ~ P^ R • • r" 

 and consequently 



R = C; 



R = C'-^, (4.) 



which equation, as it agrees with (3.)) represents a conic sec- 

 tion, whose parameter, 2 C, is determinable from the initial 

 circumstances of the motion. 



LXXIII. Reviews, and Notices respecting New Books. 



The Botanist ; containing accurately Coloured Figures of tender and 

 hardy Ornamental Plants, with Descriptions. Conducted by B. 

 Maund, F.LS., assisted by Professor Henslow, 4to. To be con- 

 tinued Monthly. No, I. 



TN the progress of science there occur periods when the establish- 

 -'- ment of works devoted to any of its branches, upon new plans, be- 

 comes absolutely necessary, in order to promote its advancement, by 

 being conformable to the improvements already achieved. Former 

 works cannot so easily be moulded to the changing conditions of 

 modern science as new ones can be accommodated to its state at the 

 time of commencing their career. Hence, in the science to which 

 the work refers, of which we have above transcribed the title, every 

 succeeding work undertaken by competent persons has been an 

 improvement upon its precursors. Most of those in existence 

 up to this time have been suited or addressed to those only who 

 were already conversant with its language and classification. But 

 an attempt is here made to render an illustrated work suitable to 

 those who have mastered its elements, and conducive to the acquisi- 

 tion of these by beginners. The terms used in the descriptions of 

 plants are in general unintelligible to the uninitiated, and therefore 

 little more is learnt by reading the description than by looking at the 

 plate. But in the work just started an explanation of every botani- 

 cal term is given, by means of a glossary, from the pen of Professor 

 Henslow, a portion of which, till it be completed, will accompany 

 each number, and to which reference can be made in every case of 



2X2 



