470 REPORT OF NATIONAL MUSEUM, 1904. 



the series it caine, thus indicating a great advance over any of his pre- 

 vious reports. 



His views on metamorphism and the production of schistose and 

 slaty cleavage were still, however, in an immature state.' It is to be 

 noted, however, that all through his work he is far from being- dog- 

 matic, usually contenting himself with a discussion of, and full quota- 

 tions from, the expressed opinions of others, stating his reasons for 

 adopting or rejecting any one, as the case ma}^ have been. 



Referring to the agencies of metamorphism, and particularly the 

 chemical changes involved in the "transfer of ingredients from one 

 part of a mass to another," he wrote: "We know of no other agency 

 by which this could be produced, except by galvanism." To the same 

 agency he would ascribe the production of cleavage, foliation, and 

 joints. He nevertheless recognized the possibility of the metamor- 

 phism of sediments through pressure, and dwelt in considerable detail 

 upon the elongation and flattening of pebbles in the conglomerates 

 near Newport, Rhode Island. The jointing of rocks in these conglom- 

 erates he regarded, as already stated, as due "to some polar force such 

 as heat or galvanism. Mere shrinkage could not have separated the 

 pebbles so smoothly, much less could a strain from beneath have thus 

 fractured them. * * * A mere inspection of the rock in place will 

 satisfy anyone that no mechanical agency is sufficient to explain these 

 phenomena." Yet to-day "mere inspection"''' will satisfy anyone that 

 mechanical agency is amply sufficient. (See also p. 510.) 



He regarded feldspar in all of the crystalline rocks as the result of 

 a process of metamorphism: 



Silicates probably furnished the ingredients, which, being abstracted by hot water, 

 left the excess of silica in the form of quartz, and formed the feldspar and mica to 

 fill up the interstices. The feldspar, which has converted the cement into gneiss, 

 could have no other origin, and this fact, in connection with all the rest which have 

 been adduced, forces a presumption that feldspar in nearly all the crystalline rocks, 

 stratified and unstratified, is a product of metamorphism. 



Further on, he wrote: 



Metamorphism furnishes the most plausible theory of the origin of the Azoic 

 stratified rocks, which are mica, talc, and hornblende schists, gneiss, serpentine, 

 white limestone, etc., such as cover a large part of Vermont. 



He recognized at this time the influence of water as an essential 

 constituent of the trappean rocks, since the intrusion of the material, 

 often in thin sheets scarcely thicker than writing paper, could not be 

 explained on the theory of fusion from dry heat alone. " By means 

 of water the materials could be introduced wherever that substance 

 could penetrate." 



His ideas concerning the origin of the drift had been considerably 

 modi tied since his earlier reports, though he was not as yet willing to 

 accept the theory of a continental ice sheet. Thus: 



