Correspondence — Mr. JR. M. Deeley. 287 



■have the strata bent and folded in sucli a manner as to cover a much 

 smaller area of country than that upon which they must have been 

 deposited. It has not, however, yet been conclusively demonstrated 

 how such thrust is produced. The hypothesis that cooling and 

 consequent contraction is a sufficient cause has been shown to be 

 untenable ; the amount of compression such a contraction is capable 

 of producing being quite insufficient to cause the amount of rock- 

 folding required to produce our great mountain ranges. 



As far as I am aware, no other theory based upon a possible 

 reduction in the diameter of the earth has been advanced which 

 seems satisfactory. In default of such an explanation I would 

 suggest that we assume that over large areas of the earth's surface 

 there is an actual expansion of the crust, such expansion compressing 

 the weaker portions into the folds forming mountain ranges. 



A probable cause of such an expansion of the crust I should like 

 to draw attention to. It may, perhaps, have been suggested before, 

 but if so I do not remember to have seen it. 



As profound changes in the physical features of the earth's surface 

 have been produced by apparently insignificant agencies, we must be 

 prepared to find that some agency which at first sight seems quite 

 inadequate is really the one which is producing the results. 



A simple experiment will illustrate the theory I wish to suggest 

 for consideration. If a strip of thin sheet lead have two lines 

 drawn across it near the ends, and it be rolled up into a coil about 

 one inch diameter, and then flattened out again, the bending will be 

 found to have lengthened it about 0-2 per cent., and each time the 

 operation is performed further lengthening will be produced. If 

 continued flexure is capable of expanding slips or sheets of lead and 

 many other materials, it may be argued that the earth's crust may 

 undergo extension under the slight flexures the sun and moon 

 produce. Under such flexure it is conceivable that vertical joints 

 might have mineral matter thrown down in them, as they partially 

 opened and closed, and mineral veins of various kinds be thus 

 formed. Or when the pressure at any point is relieved by flexure, 

 matter previously in solution might be thrown down and not be 

 redissolved when the pressure again came on. 



It would be interesting to consider the relationship mountain 

 ranges bear to the great plains where it is conceivable expansion 

 is taking place and to the positions of maximum distortion the sun 

 and moon could produce. Some connection there certainly appears 

 to be between the positions of mountain ranges, the great plains, and 

 the direction of the axis of the earth. 



As the moon always presents the same face towards us, unless the 

 sun would be a sufficient cause, there should be no great mountain 

 ranges similar to those on the earth. Indeed, on the moon the 

 surface features are apparently produced by volcanic eruptions and 

 ejections of rock or dust into a very attenuated atmosphere. 



E. M. Deeley. 



Melbourne House, Osmaston Egad, 

 Derby. 



