WESEL AND WEBER BROWN-COAL FLORA. 5 



The first is inherent to the producing- creating force, and is so far 

 independent as the force itself is independent. The second depends 

 on outward circumstances, which, however, always advance in a 

 parallel direction with that force, and render possible the existence of 

 more and more perfect beings in the same degree as those are pro- 

 duced by the former. But, whilst on the whole both work pro- 

 gressively, parallelly, and simultaneously, the positive law is in 

 individual cases frequently modified by the negative, inasmuch as 

 those organic beings for which the outward conditions of existence 

 are not suited not only cannot exist, but cannot even be produced 

 or created. The condition of creation must, therefore, accurately 

 coincide or be identical with the condition of maintenance ; the 

 creating force must coincide with the maintaining force, although the 

 maintaining conditions are not always necessarily producing con- 

 ditions." 



It would far exceed the limit of this notice to follow the author 

 through the proofs and reasonings by which he endeavours to esta- 

 blish the laws which we have laid before the reader, and which he 

 considers proved by a careful study of every branch of natural 

 history ; but we must, in conclusion, state that it is impossible to 

 open a single page in this interesting work without being struck 

 with the deep research which it evinces, or without deriving 

 information from the numerous facts which are so harmoniously 

 brought together in confirmation of his views. The chapter on 

 " Species," p. 227, is in the present state of the discussion of that 

 subject particularly deserving of notice. [W. J. Hamilton.] 



A New Contribution to the Tertiary Flora of the Brown-coal of the 

 Lower Ehine. By Dr. P. Wesel and Dr. 0. Weber. 



[Neuer Beitrag zur Tertiar Flora der Niederrheinischen Braunkohlenformation. 

 Von Dr. Phillipp Wesel und Dr. Otto Weber, zu Bonn (with 11 Plates). 

 Cassel, 1856.] 



This is an important contribution to our knowledge of the rich 

 Tertiary Flora of the Brown- coal formation on the Lower Rhine. 

 Whatever judgment we may form as to the value and authority of 

 generic and specific determinations of plants from the leaves alone, 

 there can be no doubt as to the great service done to science by the 

 publication of careful descriptions and well- executed figures of these 

 remains, which will afford most valuable materials to all future 

 investigators. 



The abundance and variety of vegetable remains in the tertiary 

 formation in question appear to be very remarkable. The greatest 

 part of them are merely detached leaves, but often in an excellent 

 state of preservation, insomuch, in some cases, that the microscopic 

 structure of the epidermis, with its pores, can be satisfactorily exa- 

 mined and compared with that of recent leaves. As many as 111 

 distinct forms (considered as so many species) are named and described 

 (mostly for the first time) in the present work ; but, it appears, from 



