28 MICROSCOPIC ILLUSTRATIONS. 



tical sections of which I have at some expense and 

 trouble lately introduced,) what a volume of instruction 

 may be derived from them ! whilst the exquisite beauty 

 arid lace-like form of the transverse cuttings will bid de- 

 fiance to every attempt at describing them ! 



In order that this class of microscopic objects may be 

 rendered as useful as possible, it may not be unimportant 

 to suggest that collections of thin sections of woods should 

 be selected according to the natural arrangement of 

 plants. In the cases I have lately mounted, an example 

 is given from all the principal groups ; and where the 

 genera, in any natural Order, are very dissimilar, two 

 specimens are taken, for the purpose of instituting a 

 comparison between them. 



I need hardly mention how essential is the aid of the 

 microscope to the Mineralogist in determining the 

 crystalline structure of a body. In the study of crys- 

 tallography, which science may be said to have been for 

 a long time almost at a stand-still, a very extensive field 

 of research appears to be now opening by the adaptation 

 of polarized light to a microscopic examination of minute 

 crystals, thus eliciting a great variety of curious and 

 beautiful properties, entirely unknown to the world be- 

 fore. This subject being as yet completely in its infancy, it 

 would be unfair to expect an elucidation of it at the present 

 time. To convey, however, some general idea to the reader 

 of the additional degree of interest which attaches to the 

 phenomena of crystallization by this happy contrivance, it 



