A. J. Jukes-Browne — Solution in Valley-making. 531 



Evenlode has been determined by a double set of joints ; *' percolating 

 water," lie says, " will reach a master -joint or a series of master-joints 

 and dissolve out a winding course underground. The water from the 

 neighbouring joints will gradually tend to leak into the master- joint 

 line, and thus a winding area of weakness will be established which 

 tends continually to widen. The ground above this weakened line 

 will slowly subside, and at length the weakened material will be 

 entirely removed, exposing the stream" (op. cit., p. 341). 



This proposition assumes that the rocks of the district are traversed 

 by a double set of joints which coincide approximately with the 

 windings of the streams, but no evidence is adduced to prove that 

 this is actually the case, and his own map shows that the windings of 

 the Glyme and the Evenlode are so irregular that they cannot be 

 reduced to the intersection of two sets of lines. This map is repro- 

 duced on the opposite page, so that the reader can judge for himself. 



Again, it is assumed that a fairly equal amount of subsidence, will 

 take place along the whole course of the supposed underground stream, 

 the result being that a surface -valley is produced which exhibits such 

 an extraordinary resemblance to a graded valley of erosion that no 

 one has hitherto suspected it to be anything else. I should have 

 expected the subsidence to have been very unequal. 



Mr. Spicer appears to have been afflicted with ghosts, and to have 

 suffered from some form of erosion-nightmare as badly as Sir Henry 

 Ho worth suffered from his ' Glacial nightmare,' for the former writes, 

 evidently with a sigh of relief, " the spectre of erosion which appears 

 to haunt almost every valley upon the earth's surface must, I think, 

 be banished from the Great Oolite plateau." If Mr. Spicer will 

 examine his ' spectre ' a little more closely I think he will find it to 

 be a very real and effective power, and not by any means a mere 

 deceptive phantom. 



Mr. Spicer thinks that "the valleys under consideration have no 

 single confirmatory mark of erosion," and that " there is no sign of 

 the past existence of any surrounding heights sufficiently great to have 

 produced streams strong enough to carve out the valleys by mechanical 

 erosion. The whole region appears to have been never anything but 

 a gently-tilted plateau." 



Does he, therefore, imagine that the rain falling on the surface of 

 this plateau has never gathered into surface-streams, even during the 

 great Glacial era of frost, snow, and rain, and that running water has 

 never accomplished any erosion in this particular district ? Does he 

 imagine that this plateau was the same in Miocene and Pliocene times 

 as it is now, that it never extended further west, and that the Oxford 

 Clay never spread over the area through which the Glyme and the 

 Dorn now run ? Has he not completely ignored the significant 

 testimony of that outlier of Oxford Clay near Tackley, which he has 

 nevertheless been careful to insert on his map ; and the other outliers 

 of the same clay to the west of Evenlode, which are omitted from 

 his map ? 



Three of the omitted outliers occur in the area where the words 

 "Lower Oolites " are engraved on the map, and there is another large 

 one to the west of "Woodstock Lake. These outlying tracts enable us 



