Mr. Weaver on Older Sirati^ed Rocks of North Devon, 109 



of that force in different latitudes must be taken into account, 

 nothing more is requisite than to multiply by the proper 

 factor. When this is done the foregoing expression will be 

 identical with the usual formula, all its minutest corrections 

 included. But there is this difference between the two cases, 

 that the usual formula is investigated on the arbitrary suppo- 

 sition that the temperature is constant at all the points of an 

 elevation, and equal to the mean of the temperatures at the 

 two extremities ; whereas the other expression is strictly de- 

 duced from the general properties of an atmosphere in equili- 

 brium. The exact theoretical formula has been made to co- 

 incide with the approximate one, by dismissing all the terms 

 that cannot be estimated in the present state of our know- 

 ledge of the phsenomena of the atmosphere. 



All the properties of the atmosphere that have been ascer- 

 tained with any degree of certainty, have been made known 

 to us by the application of the barometric formula: it would 

 therefore be superfluous to attempt, by the consideration of 

 particular experiments, any further elucidation of a theory 

 which is, in a manner, identical with observation, as far as our 

 knovvledge extends. 



[To be continued.] 



XXIII. On the Older Stratified Rocks of North Devon, isoith 

 correlative Remarks concerning Transition or Protozoic Re- 

 gions in general^. By Thomas Weaver, TLsq^.^ F.R.S.f 

 F.G.S., M.R.l.A., Sj-c. S^c. Communicated by the Author, 



IN tlie more recent views set forth by Professor Sedgwick 

 and Mr. Murchison on the Classification of the older stra- 



* Objections have been repeatedly taken to the use of the term transi- 

 tion so-ies or system, but I think without sufficient reason; for it is not just 

 to argue from the abuse against the use of anything. To its original full 

 and legitimate import I adverted upon a former occasion (in a note to the 

 8th § of my Memoir in vol. i. second series of Geol. Trans.), as denoting 

 all fossiliferous rocks of an origin antecedent to that of the Old Red Sand- 

 stone. Being in this its pristine sense a defined collective term, it is as 

 such highly useful, whatever subdivisions it may be thought right, now or 

 hereafter, to adopt, whether under the denomination of Silurian, Cam- 

 brian, or other geographical designations. Wherever these subordinate 

 distinctions may be found strictly applicable in other countries, there they 

 may be api)ropriatcly employed, for the sake of greater clearness and pre- 

 cision ; but in all cases of doubt aff"ecti«ng any portion of the series, and as a 

 term of comprehensive meaning, embracing all its members, the expression 

 transition system might yet retain its place in geological language ; unless 

 geologists in general should prefer the term j^rotozoic or jialcsozoic, the former 

 as lately proposed by Mr, Murchison, and the latter by Prof. Sedgwick. 

 The chief objection to the term transition, as it appears to me, is, that it 



