190 Correspondence — Prof. E. Hull — Mr. A. Tylor. 



by the Rev. 0. Fisher, in your last Number. As that gentleman 

 expresses the opinion that my views are based on work " in the 

 library and museum," I may be permitted to state that for more than 

 twenty years I have devoted much time and labour to the study of 

 the section in question. During that period I have measured it 

 down, bed by bed, at least a dozen times, and it may be some com- 

 fort to my critics to inform them that the results arrived at, on 

 various occasions, differ almost as greatly as do theirs from one 

 another, and from the earlier sections of Dr. Wright, the Geological 

 Survey, etc. Indeed, as I have stated in my paper, my prolonged 

 study of the section has impressed me with a profound distrust as to 

 the constancy of particular bands in these variable estuarine deposits. 

 It is true that in addition to working at the English sections, I have 

 visited the deposits of equivalent age in France, Belgium, Germany 

 and other countries, that I have examined very large collections 

 made from these deposits, and placed in Continental museums, and 

 that I have even gone so far as to carefully study the works of 

 foreign geologists which bear upon the question. But I hope that 

 Mr. Fisher is the only geologist who will regard such action as con- 

 stituting a disqualitication on m}^ part. In conclusion I must express 

 my regret that your correspondent has such a poor opinion of the 

 natives of the Isle of Wight as to suggest that the amenities of con- 

 troversy are not to be expected from them. My ancestors for many 

 generations lived in the island, and though, owing to circumstances 

 over which I had no control, I cannot claim the distinction of being 

 a native myself, yet I feel almost as jealous of any slur being cast 

 upon their good name, as if I had not been born, just across the 

 Solent, in the adjoining island of Great Britain. John Judd. 



LAURENTIAN EOCKS OF DONEGAL. 

 Sib, — Permit me to withdraw the last paragraph in page 132 of 

 my letter which appeared in the Geological Magazine for March, 

 and to express regret for having allowed myself to pen it. 



Geological Survey of Ireland, EdwAKD Hull. 



14, HujiE Street, Dublin, Wi March, 1882. 



RATE OF DENUDATION OF THE LAND BY RIVERS. 

 Sir, — In answer to your correspondent, " McJames," writing from 

 India, in your March Number, I may remark that Prof. Hopkins 

 only published one paper on the " Transport of Erratic Blocks," 

 and if your correspondent had referred to that paper he would 

 have seen my calculation was correct, see page 233, vol. viii. Cam. 

 Phil. Trans, line 3. Mr. Hopkins writes: "Therefore the moving 

 force of a current, estimated by the volume of weight, of the mass, 

 of any proposed form, which it is just capable of moving, varies as 

 the 6th power of the velocity." As 729 is the sixth joower of three, 

 my calculation in your journal of an increase of 729 times was 

 therefore perfectly correct, although by a printer's or a clerical error, 

 the fifth power of 3 was inserted instead of the sixth power of 3. 



