676 Correspondence — Mr. T. Mellard Reade. 



" views " on the rocks until after the examination of years, and 

 the views first published are those I believe in still. In the Times 

 report of the Brit. Assoc. Meeting, York, an Archeean geologist 

 called me a geological Ishmael. I think, however, if he had called 

 me a Knox or a Luther or a Calvin, this name would have been 

 more appropriate ; my hand not being against every one ; but only 

 against those that promulgate errors. 



Otoca, Nov. ith, 1881. G. H. KiNAHAN. 



RATE OF DENUDATION OP LAND BY RIVERS. 



Sir, — Mr. Tylor's astounding calculation, that during the 

 "Pluvial" period "the mean denudation" of the land was nine 

 inches per annum, or 729 times its present rate, has filled me and 

 probably other geologists with profound astonishment. Having just 

 perused Mr. Darwin's most excellent book on Mould and Earth- 

 worms, it has occurred to me to ask Mr. Tylor to suggest what 

 became of earthworms during his " Pluvial " period. Mr. Darwin 

 calculates that ten tons of earth per annum per acre is frequently 

 brought to the surface in the form of worm casts, and that the super- 

 ficial soil has passed again and again tJirough the bodies of the loorms. 

 Nine inches of soil over an acre of land would weigh, at a carter's 

 estimate of one cubic yard to the ton, not less than 1210 tons. 



No mould could possibly form under these circumstances, except 

 perhaps in deltas, as it would be removed 100 times as fast as made. 

 But I am really understating Mr. Tylor's estimate, as his nine inches 

 of denudation means solid rock, or nearly double, or say 2000 tons 

 per acre per annum. T. Mellard Eeade. 



Park Corner, Blundellsands, 

 Nov. 9th, 1881. 



LAURENTIAN (?) ROCKS, IRELAND. 

 Sir, — In the epitome of the paper read on these rocks at the Brit. 

 Assoc. York, by Prof. Hull, you end it by stating that I suggest there 

 are Laurentian rocks in the Co. Tyrone. I cannot understand why 

 I am to be made an advocate in favour of the present Laurentian 

 mania. More especially as in my paper read before the Koyal Irish 

 Academy, and in a recent paper in the Geol. Mag., I believe I have 

 brought forward good reasons for supposing these Tyrone rocks to 

 be of Cambrian age. G. Henry Kinahan. 



OvocA, Nov. 5. 1881. 



:]yniscEnLx.jL3^EO tjs. 



The Geological Survey. — In the Geological Magazine for 

 January, 1881, we di-ew attention to some recent Parliamentary statements concern- 

 ing the Geological Survey. Since then Mr. Mundella has announced that the solid 

 Geological Survey of England and Wales on the one -inch scale will be completed in 

 two years and a half, while a considerable portion of the solid and superficial Survey 

 of Ireland will be completed in seven, and that of Scotland in eleven years. He was 

 informed that the re-survey for superficial geology of those areas of England which 

 were originally surveyed for solid geology alone, would take about twenty years. It 

 was hoped that within the next few moaths the re-organization of the staff for 

 remaining surveys would be completed, and no efforts would be spared to finish the 

 work at as early a date as possible. — Standard, Aug. 19. 



