2.tS 01 sen at ions on Dr. Richardson's Paper respecting 



concurrence as to them. It gives me great pleasure there- 

 fore to find, the results of my observations on the denudated 

 districts in Sussex, Derbyshire, &c, communicated fully 

 to numerous friends within three years past, which are 

 shortly alluded to in your volumes (xxviii. p. 120: and 

 xxxi. p. 37), and more fully explained under the article 

 Denudation, and others, in Dr. Rees's New Cyclopaedia, thus 

 fully confirmed by Dr. Richardson's able investigations, 

 conducted, as far as I am acquainted, without any know- 

 ledge of what I have been doing, and tending to remove all 

 doubts as to the regular stratification of basalt. 



The cutting and carrying off of the upper strata, observ- 

 able in numerous instances in the north of Ireland, has been 

 termed by Dr, R. (pages 114, 196,) abruptions of the 

 strata, which word I am not inclined to adopt instead of 

 denudations already explained, as above. The word hum- 

 mock, introduced by Dr. R., notwithstanding the seamen 

 have limited its use to circular knowls or points of hills, may 

 have its meaning as a geological term extended, as Dr. R. 

 has done, to include such as are precipitous and irregular 

 also in their shape, and as such I shall hereafter adopt it, 

 instead of cap, (a term much too numerous in its meanings 

 already,) which I have hitherto used, in pointing out to my 

 friends in Derbyshire, the numerous hummocks on their de- 

 nudated hills ; where these detached pieces of strata, being 

 mostly accessible on all sides, have furnished the strongest 

 evidence both to myself and others on the spot, (as similar 

 ones have done in Ireland to Dr. Richardson,) that the in- 

 tervening parts of the same stratum, once continuous, have 

 .been torn off from our globe. 



Before I had ever seen a hummock or heard of a denu- 

 dated district, from observing the universality of fissures 

 or faults in Bedfordshire, having their sides always po- 

 lished or worn, pursuing rectilinear courses, quite incon- 

 sistent with the crater-like action of any force hitherto sup- 

 posed to have acted from below, I was irresistibly led to 

 the consideration of forces acting from above, as Dr. R. has 

 also been, by the evident excavation of valleys and leaving 

 of hummocks in his basaltic area. 



The 



