524 Correspondence — Prof. Hull, etc. 



BOULDER-CLAY IN IRELAND. 



Sir, — I can assure Mr. Birds that he is perfectly correct in sup- 

 posing that there is an Upper Boulder-clay in Ireland, resting on 

 "Middle Sands and Gravels;" and these again on the Lower Boulder- 

 clay or Till. The general series is precisely similar to that of the 

 North-west of England, to which he refers in his letter in the Geol. 

 Mag. for September last (p. 429). If former sections which I had 

 examined had left any doubt on this question on my mind, it would 

 have been removed on seeing the section of the Post-Pliocene beds 

 laid open at the marble quarries of Kilkenny, shown to me this 

 summer by Mr. Hardman, of the Geological Survey. This and 

 other sections in the district tend to prove that the Upper Boulder- 

 clay occupies a considerable extent of surface in that part of Ireland. 

 As this fine section will probably be described in detail by Mr. 

 Hardman himself, I shall not further allude to it, than to say that 

 it puts out' of court any future attempts to call in question the 

 succession of the Drift series as given above. 



The " Esker Drift " so-called, I consider to be later than the Upper 

 Boulder-clay, and is only a remodelled form of the true Drift-beds. 

 5, Raglan Road, Dublin, 10 Sept. 1875. Edward Hull. 



MR. BONNET ON GLACIAL EROSION. 

 Sir, — On this subject, in this month's Number, Mr. Bonney is as 

 full of sound sense as usual. But as regards the widening of upland 

 valleys I wish that I could persuade him that there is no necessity 

 for " the volume of the stream being formerly greater," or for " the 

 slow motion of the river from one side of the valley to the other," 

 and to substitute " atmospheric and rain erosion " for " fluviatile 

 erosion." I never heard of what Mr. Goodchild calls " the spring 

 theory " for forming cliffs and widening valleys. He indeed con- 

 troverts the theory, in which I most cordially agree with him. 

 But does any one hold it ? If so, who ? Springs cut channels, but 

 what widens these channels into valleys is atmospheric disintegration 

 and the erosion of rain. For this reason the same valley is always 

 narrow directly as the hardness of the strata and wide directly as its 

 softness. So in rocky strata cliffs and rock ledges will be formed ; 

 in soft strata smooth sloping sides ; but if the widening of valleys 

 resulted, as Mr. Goodchild says, from " mechanical means," the soft 

 strata should form cliffs and ledges as well as the hard ones. 

 Beookwood Park, Aleesfoed, George Greenwood, Colonel. 



15th September, 1875. 



Geological Survey of India. — We are glad to be able to an- 

 nounce the promotion of Mr. King to the first grade of this depart- 

 ment, and of Messrs. Hughes and Willson (the latter formerly of 

 the Geological Survey of Ireland) to the second grade. We are 

 also glad to see that Dr. W. Waagen has succeeded to the separate 

 appointment of Palaeontologist left vacant by the lamented death of 

 Dr. Stoliczka. With Dr. Waagen and the recent additions to the 

 staff of Mr. K. Lydekker and Dr. 0. Feistmantel, the Indian Survey 

 may be congratulated upon its great palceontological strength. 



