30-1 



:, AS I L. 



seven in number, assembled round a larger and cen- 

 tral column, which they appear to be connected with ; 

 while the causeway pillars are not observed to respect 

 any point or centre, but are each independent and 

 complete. The basalts of these rocks also abound 

 in small crystals, not unlike rock crystal, but much 

 softer, and which yield to the action of the air. 



The promontory of Castel d'laci, which terminates 

 the basis of Etna, is almost entirely composed of 

 basalts ; but of a different kind from what has been 

 just described. It consists of a number of cylinders, 

 whose diameters vary from six inches to twenty feet. 

 Some of these are solid, others hollow like a cannon ; 

 some extended in layers, others compressed like rolls 

 of tobacco , some are like globes inclosed in the 

 rocks, while others are bent in a variety of forms. 



A general view of the various theories illustrative 

 of the origin of basaltic formations, will be given 

 under the head of TRAP-ROCKS, called by geologists 

 " unstratified superjacent ;" and we must content 

 ourselves, in the present place, with briefly adverting 

 to one or two hypotheses, which are essential to the 

 illustration of our present article. Mr. Hare, who 

 devoted a considerable deal of science and industry to 

 an examination of the Antrim formations, says, that 

 where basalt does not divide itself precisely after the 

 manner of prismatic columns, or evince a tendency 

 to that figure on a great and general scale, it often 

 forms laminated spheroidal bodies, which, varying in 

 their diameters, constitute, by aggregation, rocks of 

 considerable magnitude. 



The latter circumstance, in addition to the occur- 

 rence of basaltifc fragments, in which a sphere appears 

 to be enveloped by a polyhedral figure, suggested the 

 idea that a compressible laminated sphere must be the 

 primitive figure of each prismatic articulation, compos- 

 ing a common basalt ; and that the lateral plane surfaces, 

 as well as the corresponding concavity and convexity 

 of the horizontal surfaces, the trihedral processes of 

 the lateral edges, and the corresponding truncations 

 of the superimposed joint, result from the assemblage 

 of spheres under the influence of gravitation while 

 the component particles are in a yielding state ; their 

 laminated structure being a mechanical accommoda- 

 tion to the filling of those interstitial spaces, which 

 must result from an aggregation of spheres. 



Basaltic Columns. 



These ideas may be in some degree elucidated by 

 the accompanying engraving, in which the first figure 



represents a basaltic fragment from the vicinity of 

 Belfast, where the sphere is developed by a partial 

 decomposition of the prisrn ; while the group shows 

 the prevailing character of basaltic columns in general, 

 two of the constituent prisms being detached, to show 

 the alternate concavity and convexity of the horizon- 

 tal surfaces, with the angular surfaces and truncations 

 of their edges. 



The Rev. William Conybeare thus describes his 

 view of the basaltic formations : " I would observe, 

 then, that this formation is distinguished by charac- 

 ters so directly opposed to those which all rocks 

 undoubtedly of aqueous origin possess, that no 

 hypothesis which ascribes both to a common origin, 

 can be otherwise than contradictory, and at variance 

 with itself. For, 



" 1. Of all other formations, the least ancient an; 

 the least elevated ; but this, the most recent of all, 

 yet rivals the primitive mountains in height. 



" 2. Of all other formations, the degree of consoli- 

 dation decreases together with their age, their texture 

 passing from crystalline through the several grada- 

 tions of sub-crystalline, compact, coarse, and lastly 

 earthy ; while in this formation, even where it rests 

 on chalk, the crystalline texture of the oldest rocks 

 frequently occurs. 



" Whin dykes, which are indisputably connected 

 with this formation, differ from all other mineral veins 

 in the circumstance of their traversing all rocks indif- 

 ferently ; while of other veins, particular classes are 

 exclusively associated with particular rocks. S-.ich 

 being the negative evidence against the Neptunian 

 hypothesis, I proceed to that which is positive in 

 favour of the Volcanists ; as, 



" 1 . The identity of chemical composition in basalt 

 and lava. 



" 2. The constant occurrence of trap-rocks in vol- 

 canic districts. 



" 3. The confessions of the Wernerians themselves, 

 that the basalt of Auvergne is one of igneous origin. 



fc 4. The testimony of those best acquainted with 

 districts still exhibiting active volcanoes. Such per- 

 sons as Dolomieu and Spallanzani, have uniformly 

 maintained the igneous origin of basalt, while those 

 who have contended against it, have generally been 

 practically unacquainted with countries of this descrip- 

 tion." 



Whether, with the above distinguished geologist, 

 we regard the basaltic masses we have described, as 

 of igneous formation relics of those tremendous 

 volcanic operations which shook the whole world, 

 and ultimately, by breaking up the foundations of the 

 great deep, assisted in producing the deluge recorded 

 in Holy Writ ; or whether we adopt the less assum- 

 ing theory of an aqueous origin, the contemplative 

 philosopher must see in their exquisite symmetry of 

 arrangement and magnificence of architectural pro- 

 portion, a new cause for reverential gratitude to the 

 great Architect of all things. 



Who not content 



With every good of life to nouiish man, 

 By kind illusions of the wondering sense. 

 Hath made all nature beauty to the eye, 

 And music to the ear. 



BASIL. The Ocymum basilicum of Linnaeus. 

 This is an extremely sweet-scented garden pot-herb, 

 and being an annual is sowed every year on a warm 

 border, thinned and Kept clean, is ready for gather- 

 ing when in flower, and then, gradually dried, is tied 

 in small bundles and hung up in a dry room for use. 



