316 Dr Murray on a Deposite of Foreign Plants, 



pact prehnite, and even the serpentine of Banffshire ; and occa- 

 sionally bones of extinct quadrupeds, as the tusks and molares of 

 the fossil elephant ; while rounded nodules of agate, mocha stone, 

 and jasper, also abound in the same gravelly beds, broken up 

 by the tides and wintry storms. 



But in viewing such diluvial coverings of ancient date and 

 extensive range, we must be careful not to confound with them, 

 local and far later depositions, the effects of partial and general- 

 ly of fresh water inundations. The bursting of a lake, the 

 change in the course of a river, or the transitory passage of 

 some wintry torrent, leave a wreck behind them of gravel, mud, 

 and fragments of stony masses swept from distant hills, which 

 may locally cover the strata for a short distance, and contain 

 bones and shells far more recent than those occurring in that 

 universally diffused gravel every where to be met with. 



As in all sciences, so in geology, it is hard to say whether 

 more harm, more hinderance, have arisen from too great a spi- 

 rit of generalisation, or from views too partial and narrow. 

 Thus in the " Theory of the Earth,'^ the first writers, led away 

 by the fascination of the subject, built up their cobweb reveries, 

 their gilded dreams, upon a few isolated and doubtful facts. 

 More recent geologists have perhaps erred on the other hand ; 

 and, dreading the ridicule and reproach attached to their pre- 

 cursors, have amassed numerous and valuable materials, without 

 an attempt to compare or to combine. The survey and obser- 

 vation of one district, or even of one kingdom, will never suf- 

 fice ; the united and judicious comparison of many and distant 

 countries can alone lead to any thing like a grand, comprehen- 

 sive, and accurate map of the rocky structure of the earth. Par- 

 ticular links in the great series of strata may be lost or observed 

 in one country ; but this must be rectified by attentive surveys 

 of the order of position in another, and by what shades one for- 

 mation passes into another. 



When such enlarged views, such connected investigations of 

 the rocky bases of different countries shall have been made, we 

 may not still indeed possess a full and incontrovertible system of 

 all the changes which this planet has undergone, but we shall 

 have more precise and philosophical terms, whereby to denomi- 

 nate the strata and deposites originating from these changes ; and 



