PROCEEDINGS FOR 1896 LXXXVII 



The important influence and the energetic work of tlie youngest 

 member of the "combine" in the building up of the lithosphère has 

 already been referred to, and we may now add the not less important 

 work of pulling down also. Destruction and construction is a natural law. 

 It is universally adopted and practised by man ; but whether he oi)])oses 

 it or aids it, the law is there, and will be inevitably carried out in that 

 circular form which symbolizes all nature, and has, so far as we are con- 

 cerned, like the circle itself, no beginning and no end. Nothing is de- 

 stroyed, but change or metamorphism is continuous, however slow and, to 

 our defective senses, inappreciable it may be. 



I shall now make some further remarks on what appear to me to 

 have been the direct effects of the work referred to. We must bear in 

 mind, in this matter of evolution or building up, the primary necessity of 

 materials ; and the question at once arises, whence came these needed 

 materials ? The answer is, primarily from the solid and perhaps still hot 

 crust of the litViosphere, and, secondarily, from the continual decay, dis- 

 integration and transposition of matter by the internal and external action 

 of the then slowly developing hydrosphere. And here I may record my 

 opinion that to those actions ma}' be ascribed the commencement of vol- 

 canic activity, and that neither it, nor its important results are in any 

 degree due to central heat, as is still, [ believe, held by many, and half a 

 century ago was regarded as a geological axiom, though Lyell about that 

 time wrote: ''There appears no sound objection to the doctrine that 

 chemical changes, going on at various depths in the earth, may be the 

 cause of volcanic action.'" 



In accordance with the foregoing ideas of the evolution we are 

 tracing, it is in the records that are left us o"f the Upper Archa-an or 

 Huronian rocks that we look for, and we certainly find, the first unmis- 

 takable evidences of the combined action of oceanic and volcanic, or erup- 

 tive and irruptive, and aqueous abrasive and sedimentary forces. 



Far too large a share of the work of providing constructive materials 

 has, however, in the past been credited to the ocean and far too little to 

 the atmosphere and to the volcano. Its muds, its ashes, its lavas, its 

 breccias, its conglomerates, its waters and its gases, except in British 

 geology, have scarcely been recognized, especially tho.se of Archu'an 

 and Palaeozoic times. Dana sa3's, •■ Volcanic eruptions have added a 

 little to the supply." ' But, then, it is only since 1871) that volcanic 

 ejectamenta of Pala-ozoic and pre -Palaeozoic times have been recognized 

 as such by United States geologists. I can best illustrate this by the two 

 following unpublished letters, the one addressed to the late Professor 

 Dana in 1879, and the other to the late Professor Gr. H. Williams in 1891. 

 They are now somewhat historical in this connection. 



1 Manual IS. 



