FREE BOOKS

Author's List




PREV.   NEXT  
|<   188   189   190   191   192   193   194   195   196   197   198   199   200   201   202   203   204   205   206   207   208   209   210   211   212  
213   214   215   216   217   218   219   220   221   222   223   224   225   226   227   228   229   230   231   232   233   234   235   236   237   >>   >|  
if I am utterly floored. P.S.--I have a presentiment it will turn out that when clay-slate has been metamorphosed the foliation in the resultant schist has been due generally (if not, as I think, always) to the cleavage, and this to a certain degree will "save my bacon" (please look at my saving clause, page 167) (542/2. "As in some cases it appears that where a fissile rock has been exposed to partial metamorphic action (for instance, from the irruption of granite) the foliation has supervened on the already existing cleavage-planes; so, perhaps in some instances, the foliation of a rock may have been determined by the original planes of deposition or of oblique current laminae. I have, however, myself never seen such a case, and I must maintain that in most extensive metamorphic areas the foliation is the extreme result of that process, of which cleavage is the first effect" (Ibid., page 167).), but [with] other rocks than that, stratification has been the ruling agent, the strike, but not the dip, being in such cases parallel to any adjoining clay-slate. If this be so, pre-existing planes of division, we must suppose on my view of the cause, determining the lines of crystallisation and segregation, and not planes of division produced for the first time during the act of crystallisation, as in volcanic rocks. If this should ever be proved, I shall not look back with utter shame at my work. LETTER 543. TO J.D. HOOKER. Down, September 8th [1856]. I got your letter of the 1st this morning, and a real good man you have been to write. Of all the things I ever heard, Mrs. Hooker's pedestrian feats beat them. My brother is quite right in his comparison of "as strong as a woman," as a type of strength. Your letter, after what you have seen in the Himalayas, etc., gives me a wonderful idea of the beauty of the Alps. How I wish I was one-half or one-quarter as strong as Mrs. Hooker: but that is a vain hope. You must have had some very interesting work with glaciers, etc. When will the glacier structure and motion ever be settled! When reading Tyndall's paper it seemed to me that movement in the particles must come into play in his own doctrine of pressure; for he expressly states that if there be pressure on all sides, there is no lamination. I suppose I cannot have understood him, for I should have inferred from this that there must have been movement parallel to planes of pressure. (543/1. Prof. Tyndall had published p
PREV.   NEXT  
|<   188   189   190   191   192   193   194   195   196   197   198   199   200   201   202   203   204   205   206   207   208   209   210   211   212  
213   214   215   216   217   218   219   220   221   222   223   224   225   226   227   228   229   230   231   232   233   234   235   236   237   >>   >|  



Top keywords:
planes
 

foliation

 

cleavage

 
pressure
 
metamorphic
 
Hooker
 

division

 

suppose

 

existing

 

strong


parallel
 
Tyndall
 

movement

 

letter

 

crystallisation

 

comparison

 

September

 

things

 

strength

 

pedestrian


morning
 

brother

 

doctrine

 
expressly
 

particles

 
states
 
published
 

inferred

 

lamination

 

understood


reading

 

settled

 
beauty
 
HOOKER
 

wonderful

 
Himalayas
 

glaciers

 

glacier

 

structure

 

motion


interesting

 

quarter

 
produced
 

irruption

 
floored
 
granite
 

supervened

 

instance

 
fissile
 

exposed