VOL. LXV.] PHILOSOPHICAL TRANSACTIONS. 581 



to which they adhere ; and seem to acknowledge, with them, one common and 

 simultaneous origin ; like the rhomboidal and other crystallizations in granites, 

 and other similar vitrifiable compound stones. The common slow and limited 

 principle of crystallization, seems not at all adequate to so great an effect, which 

 seems exclusively attributable to an igneous fluid, on the general concretion of 

 which, the organic principle may be supposed to have operated simultaneously in 

 a large mass, and produced these bodies in the same manner as a linget of metal 

 concretes at once in the mould. No other mode of generation seems reconcile- 

 able with the phenomena of basaltine aggregates. It seems also further evident 

 from the phenomena, that prismatic basaltine crystallizations, and other regularly 

 figured vulcanic groups, have been generated locally, and not in the midst of 

 those violent convulsions of Nature which are commonly assigned for the origin 

 of vulcanic mountains in general. That the principle of organization, whatever 

 it be, operates locally in the formation of these bodies, appears sufficiently evi- 

 dent from the regular disposition and other particular characters of their groups. 

 For notwithstanding the various directions of the columns, and masses com- 

 posed of them, in the different groups, yet in other respects the greatest 

 regularity of disposition is commonly observable. They form strata, which are 

 uniformly organized, disposed in particular directions, and often constant in the 

 same to a great extent. These strata not only manifest a parallelism between 

 their regularly figured parts, but in their whole aggregates ; which often form 

 extensive horizontal beds, and of an equal thickness throughout. This 

 parallelism is also equally remarkable in groups that are composed of many 

 strata ; as I have particularly observed in those of Murat, and the Castle Hill of 

 Achon, in Upper Auvergne ; in which the columnar strata are not only parallel 

 in themselves, but preserve in their position, a parallelism with the other strata 

 of the respective groups, which lie in regular stages, one above the other: and 

 since these groups commonly form, in a manner, integral parts of the masses, 

 or mountains in which they are found, and these manifest also some affinity in 

 their structure; it seems most reasonable to assign to both one common origin. 

 The Euganean hills form an irregular group in the plain of Lombardy, about 

 7 miles nearly south by west from Padua, and extend from north to south as far 

 as Este. The most considerable part of them composes an irregular soi-t of 

 chain, which extends in the above direction ; while other parts are severally de- 

 tached, and form isolated mountains about the skirts of this chain, particularly 

 on the north-east side, towards Abano. The outer skirt of the entire group may 

 measure from 30 to 40 English miles. The external characters of this group 

 exactly correspond with the forms commonly ascribed by naturalists to vulcanic 

 mountains in general; since the points of the chain before mentioned, as well as 

 the isolated members of it, are of various conical, orbicular, and elliptical shapes. 



