26 PKCX II DINGS OF TORONTO MEET] NTG. 



ancea which may depend on relative densities. If I have oot caught correctly the 



views : imi nations be will i -■ put me right. 



P ■:■ ( 'n a \i itK.ui.i \ : I would like to inquire to what area Mr. Gilbert limits 



the four and >ix hundred cubic mil 



Mr. Gilbert: That raises a question I hare not answered to my own tion. 



1 • to me that the imposition of a long, narrow ridge will be no more effec- 



tive in producing deformation than a small portion of the Bame ridge, but it is not 

 ir whethera broad 1 Ided matter will be ve as a more compact lens 



of the Bame weight. 



Mr. II \ v : There is a series of effects in connection with the outcrop of the Lignite 

 in the upper part of the I' Formation in Kansas, which has suggested t" me 



similar thoughts t<> thot I Mr. Gilbert. En pla the lignite is a usable variety of 



'. need locally f"r fuel. It ie worked almost entirely by drifts into the Bides of the 

 bills, :m<l in ii" case have 1 known a Bhaft or well on the high prairie adjoining to 

 strike lignite, and in tl where the mines have had any extended working it 



always thins out as it enter- the body of the hill. The lignite is the Boftest body of 

 material in the ridges, and it seems as if the removal of the pressure by the cutting 

 out of the valleys and plains has somewhat thickened it or pressed it out a little. I 

 do not know a single instance in which it has been pierced by a deep well on the 



prairie. 



P •!• Stkvknson: I would like to say a word or two incidentally. With 



res] r of shear, I think we have made a mi-take in a great many cases. 



The theory has prevailed, and does prevail very extensively still, that ordinarily fold- 

 ing has advanced bo .-lowly that, speaking in a general way. the particles of rocks 



adjusted themselves and crushing was avoided. Depending on that th y I was led 



into a grievous error, which might have led to the loss of several million- of dollars, 

 and which did lead to a loss sufficiently great to bring discomfort. After examining 

 the tunnel locations on the line of the South Pennsylvania Railway in Pennsylvania, 

 l itat d that in those passing through the Pocono sandstone, which is about 1,100 feet 

 thick in that region, very massive and apparently very Bolid, arching would not be 

 \ • dingly contracts were let for a lull double track railroad just there. 



i the tunnels were made the full width. A year later I was si at for in great hi 



the Pn tident of the Construction Company to come out there and what was 



the matter with th< Istone tunnels. Something was very wrong. The fact of 



the mal sandstone tunnel- needed to be arched more strongly than the 



tunnel- in -late. In the folding the rock had been crushed into enormous wedj 

 which had -lipped hack and forth on each other, and naturally th'' adjustment was 



■. had. That was the only shear down there, and lines which were found all along 



tie the top, containing quartz, and which had been a puzzle to many 



i to be the planes between these several wedges : and the tunnel 



in W B I ford i intj Pa bows the condition only too well, for there one 



oft a little narrower than the tunnel, and kept Bottling 



rn until at la The same condition was found 



in the other mountain r we cut through this sandstone ; the sandstone did not 



ad : a bit ue. re than th i vhicb had 1 D orushed into small tV 



menu which w< ich other and rubbi and forth until thosi 



wh ounty, P but > mass of lenticular pit 



m not much lai hand So the question of o which 



all dep. .. my mind d to be, 



