63 Introduction to Geology. 



frequently "called " naked ladies." This small order produces 

 nothing of extraordinary importance. The fourth order, 

 Hexagynia, is little better than nominal; the fifth order, 

 Polygynia, contains the water-plantain (^lisma, from alis^ wa- 

 ter, C^Z^.), of which several species are natives of this country; 

 one, A, Plantago {Jig. 13.), is very common, and might borrow 

 from the heart's ease the familiar appellation of Herb Trinity. 

 The calyx has three leaves, the corolla three petals ; the cap- 

 sules, of which there are six, are ranged in a 

 triangular form : the flower-stalk is three feet 

 high, and the upper part clothed with flowers, 

 set in whorls infinitely compounded, six in 

 each whorl, three twice the size and length of 

 the alternate three. Where this plant is 

 luxuriant, the subdivisions of the whorls are 

 innumerable. Wherever a pond is to be 

 found, the water-plantain is to be found by 

 the sides of it. It blossoms in the month of 

 July, and is seen to most advantage at about two or three 

 o'clock in the afternoon ; after that time its thin and some- 

 what crumpled petals begin to droop. 

 (To be continued.^ 



Art. XIV. Introduction to Geology. 

 (Continued from Vol. I. p. 453.) ' 

 GEOLOGICAL SYSTEMS OF ARRANGEMENT. 



It has been seen in our introductory article on the pro- 

 gress of geology, that the researches of geologists, conunencing 

 with Werner, Saussure, Mitchell, and Smith, led to the dis- 

 covery of certain laws relative to the origin and succession of 

 rocks. Various terms have been employed in their classifica- 

 tion. It was long considered sufiicient to divide them into 

 two great classes : the Primary, consisting of rocks whose 

 structure is chemical only, and possess no traces of or- 

 ganic beings ; and the Secondary., consisting of rocks whose 

 structure is chiefly mechanical, and which contain numerous 

 substances of obvious vegetable and animal origin. This ar- 

 rangement was recommended by its simplicity, and the facility 

 it affords of referring the different rocks to one or more of 

 these great divisions. 



In order to distinguish the more recent portions of the class 

 before named Secondary, a further division was suggested, and 

 the term Tei'tiary has been adopted by most geologists, as 

 designating the strata which were deposited successively over 



