On the Hill of ARTHURS SEAT. 9 



dropped from the atmofphere upon the different parts of the 

 hill, in the fhape and extent in which we find thofe ftripes of 

 withered grafs ? This laft hypothefis is not fupported by any 

 appearance that I know of in this country j and the other is not 

 confiftent with the natural appearances to which it muft be- 

 long ; for the folitary or infulated fpots, which often form part 

 of a flripe, feem to be reproduced, in nearly equal quantity, 

 each fucceeding year, without any gradual extenfion in the 

 flripe, which alfo feems to preferve its former extent, as well as 

 breadth and form. 



Therefore, when we confider the various fituations and 

 extent of thofe narrow ftripes of withered grafs, the regularity 

 to be obferved in their fhape and progrefhon, and the conftan- 

 cy which feems to take place with regard to their fucceffion, we 

 muft, at the fame time, be perfuaded, that there is a natural 

 caufe which may be invefligated for the explanation of thofe 

 appearances, and reject the mere fuppofition of caufes which do 

 not feem, of themfelves, adequate to the effect perceived. 



Great attention would be required in making obfervations 

 with a view to difcover the caufe of thofe appearances ', and 

 the difficulty of this talk is much increafed by an ambiguity 

 which occurs on certain occafions, where the breeding of in- 

 fects in confequence of the death of plants, may be miftaken 

 for the death of plants in confequence of infects ; but, on the 

 other hand, in the prefent cafe, great advantage, for an en- 

 quiry of this fort, may be derived from the opportunity that 

 there is of examining, not only what had been killed the pre- 

 ceding, but alfo that part which is, perhaps, to be killed the 

 enfuing feafon ; and where experiment may be made by cut- 

 ting off the communication betwixt thofe two parts as deep as 

 the foil may admit. 



The apparent production, or rather the multiplication of 

 fome fpecies of animals, in confequence of a certain deftruction 



Vol. II. b of 



