190 Correspondence — Mr. John Smith. 



the soil, no matter how slowly or feebly the process operates or 

 proceeds. 



(5) That such implied decomposition, deformation, destruction, 

 reunion, and new combinations of particles and substances of the 

 soil explain why some soils are more fertile than others where 

 science fails to find any difference in them ; while others prove less 

 fertile than experiment would indicate or suggest. 



(6) That the almost daily recurring changes of weather and less 

 frequent seasonal changes, both as to temperature and humidity, 

 with the help of animals, decay and finally crumble and disperse 

 exposed wood, etc., until it is gone, and suggests how thoroughly 

 the same repetition of precipitation and evaporation is also working, 

 though unseen, just below the grass. 



If this incessant oscillating or slow-motion progress of the 

 water through the soil be a fact, then I should suppose that 

 where it has operated with greatest vigour, there, other things being 

 equal, would the soil be thickest and most productive; and vice 

 versa, where the surface evaporation was most sluggish. Possibly 

 the heavy rains and intervals of high temperature of the tropics 

 account for the great fertility of their soils as much or more than for 

 their richness as regards composition. 



It will thus be seen that the leading idea in these propositions is 

 evaporation — the upward motion (capillary attraction) of the con- 

 tained-water of the soil working upon the inorganic and organic 

 solid constituents of it, in conjunction with the descent of moisture 

 in the forms of rain, snow, fog, etc. W. S. Greslet. 



P.O. Box 437, 



Erie, Pennsylvania, U.S.A. 



SECTION EXPOSED AT THE DRY DOCK, TROON, AYRSHIRE. 

 Sir, — The section of rocks exposed in the Dry Dock being con- 

 structed at Troon, Ayrshire, may be worthy of preservation in the 

 Geological Magazine. It is as follows : — 



Feet. 



A. " Forced " or Artificial material ... 8 



B. Bedded, coarse-grained trap ... ... ... ... ... 8 



C. Volcanic dust ... 7 



D. ,, „ bluish 1 



E. Grey, fine-grained, banded rock ... ... ... ... . 1|- 



F. Water of Ayr Hone stone (seen) ... ... ... ... ... 8 



A. Consisted of general rubbish, with fragments of pottery, etc., 

 but not very old. 



B. Towards the north end of the dock works this bed was much 

 thicker, having apparently at that point cut out the beds below it to 

 some depth, the " bedding" of the upper part of the trap being quite 

 regular. 



C. This bed had at one time been worked in a pit, the dock works 

 having cut through the old workings. Six feet was the depth 

 of the bed taken out by the pit, the working places being about 

 fifteen feet wide. Nothing historical is preserved as to this pit, but 

 there is a tradition that contraband goods were hid in the workings, 

 and the material from the mine — which has been called "china 



