684 SCIENCE PROGRESS 



I ask those who can read and who have read to ponder over 

 these magnificent lines ; I would urge all to begin who cannot, 

 in order that they may understand their extraordinary signifi- 

 cance. The wonderful art the poet exercises of compressing a 

 whole history into a few short sentences, the marvellous power 

 of words to excite long trains of thought, is nowhere better dis- 

 played ; but the power of the words in themselves is nil — they 

 acquire meaning only when the will exists to give meaning to 

 them. 



My object, however, in quoting Tennyson's lines is to ask you 

 to think of them as descriptive of the genesis of agricultural 

 soils. The primary soils were undoubtedly sands and clays 

 formed by the decay and disintegration of the erstwhile molten 

 crust — of rock like that known to us now as granite, made up 

 of at least three different crystalline materials : felspar, mica 

 and quartz. Quartz is indestructible except mechanically ; mica 

 is not easily affected ; felspar, however, under ordinary atmo- 

 spheric influences, is sooner or later broken down into clay 

 and soluble matters : granite therefore gradually disintegrates 

 on exposure, owing to the decay of its felspar. 



In the earliest times, as now, the clays thus formed, being in a 

 very fine state of division, would have been carried far out to sea 

 and only slowly deposited ; but the streams which conveyed the 

 clay out to sea would also grind down the mica and the quartz 

 until eventually the one was converted more or less into clay and 

 the other into quartz pebbles and sand-grains, which also were 

 conveyed greater or less distances out to sea and deposited as 

 sediment on the ocean floors : in this way, gravels, sands and 

 clays were laid down contemporaneously but in different 

 regions. The thickness of rock which underwent disintegration 

 must have been enormous, considering the enormous thickness 

 of the sedimentary rocks. 



But sand and clay are not the only rocks known to us : those 

 of you who are at home in this district are aware of the existence 

 in it of a vast mass of chalk. In what relation does this stand to 

 sand and clay ? How will you find out ? No detective attempts 

 to unravel the mystery of a crime from his armchair — he goes 

 out into the world and seeks for signs : and so must you if you 

 desire to solve the many problems which limestone presents. 



No doubt there are chalk pits to be found and the coast is 

 open to inspection. Suppose you visit the pits, hammer in 



