ROC 



ROM 



formed . When concave, they are termed 

 basin-shaped ; and if the concavity is 

 long, trough-shaped. Their upper extre- 

 mities, appearing 1 at the surface of the 

 earth, are termed the outgoings of the 

 strata : the outermost of the circles form- 

 ed by these is the oldest in the concave 

 (the basin and trough-shaped), and new- 

 est in the convex (the mantle and saddle- 

 shaped). When detached portions occur 

 on the summits of hills, they are called 

 caps ; when filling up hollow spaces, up- 

 fillings ; and when only on one side of a 

 mountain, shield-formed. 



It has been here said, according to the 

 theory of Werner, that one class of 

 mountains was deposited, by chemical 

 formation, from an aqueous solution, pre- 

 vious to the creation of vegetables and 

 animals : that to these succeeded another 

 class, in which materials mechanically se- 

 parated were discoverable, formed dur- 

 ing the passage of this globe into a habit- 

 able state ; and that during the existence 

 of animals and vegetables in considerable 

 number, another (the latest) class was 

 produced, in which mechanical deposits 

 and remains of organized bodies exist in 

 considerable quantity. Of these different 

 classes of rocks, it may be expected, that 

 the rocks of the earliest period would be 

 found invested in various modes by those 

 of later formation, and disposed in the or- 

 der of their separation from the waters 

 from which they derived their origin. 



The rocks which exist in the Hartz ap- 

 pear to be beautifully illustrative of this 

 successive deposition. In the centre a 

 vast mass of granite rises through the 

 other strata, and round this clay-slut e is 

 disposed in mantle-shaped strata. Gneiss 

 and mica-slate not existing in this coun- 

 try, transition limestone succeeds to the 

 clay-slate, and then grey wacke and grey 

 wacke slate : the whole being wrapped 

 round the granite in mantle-shaped stra- 

 ta, and invariably with lower and lower 

 outgoings, corresponding to the newer 

 and newer strata. To these the floe'tz 

 rocks succeed, the oldest of the floe'tz 

 resting on the newest of the transition ; 

 and the different floetz rocks resting on 

 each other according to their relative 

 age. Last of all, the alluvial rocks are 

 found in the lowest situations. We have 

 thus, as Mr. Jameson observes, all the 

 series of rocks, from the granite to the 

 alluvial, marked with a diminishing le- 

 vel, in proportion to the newness of the 

 strata. 



The system of Werner, formed upon a 

 omprehensive view of tho several 



phenomena observable in the formation, 

 of the crust of this globe, has been here 

 adopted, from Professor Jameson's per- 

 spicuous description of it, on account of 

 its so exactly corresponding with the ap- 

 pearances which masses of rocks every 

 where present to our view. The present 

 outline, though perhaps sufficiently cor- 

 rect, is, however, by no means pretend- 

 ed to supersede the study of the work 

 alluded to ; since an accurate knowledge 

 of the subject can only be yielded by the 

 study of the more highly finished per- 

 formance itself. 



ROCKET. See PTROTECHNY. 



ROD, a land measure of sixteen feet 

 and a half; the same with perch and 

 pole. 



ROELLA, in botany, so named in ho- 

 nour of William Roell, a genus of the 

 Pentandria Monogynia class and order. 

 Natural order of Campanacese. Campa- 

 nulaceae, Jussieu. Essential character : 

 corolla funnel-form, with the bottom clos- 

 ed by staminiferous valves ; stigma bifid ; 

 capsule two-celled, cylindrical, inferior. 

 There are five species, all natives of the 

 Cape of Good Hope. 



ROHRIA, in botany, so named in ho- 

 nour of Julius von Rohor, a genus of the 

 Triandria Monogynia class and order. 

 Essential character : calyx bell-shaped, 

 five-parted : corolla five-petalled, un- 

 equal ; stigmas three, revolute ; capsule. 

 There is but one species, viz. R. petioli- 

 flora, a native of the woods of Guiana. 



ROGUE. See VAGRANT. 



ROHAULT (JAMES), in biography, a 

 French philosopher, was the son of a 

 rich merchant at Amiens, where he was 

 born in 1620. He cultivated the languages 

 and belles lettres in his own country, and 

 then was sent to Paris to study philoso- 

 phy. He seems to have been a great 

 lover of truth, at least what he thought 

 so, and to have sought it with much im- 

 partiality. He read the ancient and mo- 

 dern philosophers; but Des Cartes was 

 the author who most engaged his atten- 

 tion. Accordingly, he became a zealous 

 follower of that great man, and drew up 

 an abridgment and explanation of his 

 philosophy with great clearness and me- 

 thod. In "the preface to his Physics, for 

 so his work is called, he makes no scru- 

 ple to say, that " the abilities and accom- 

 plishments of this philosopher must oblige 

 the whole world to confess, that France 

 is at least as capable of producing and 

 raising men versed in all arts and branches 

 of knowledge as ancient Greece." Cler-^ 

 selier, well known for his translation of 



