ON THE USE OF LIME, MARL, AND SHELL-SAND. 2? 



nearly 50 per cent., and that therefore both will prove useful 

 fertilizers upon soils deficient in lime. 



9. That the shell-sands from Comb Martin and Hartland Quay 

 are inferior kinds of sea-sand, especially the former, since it 

 contains only 14 per cent, of carbonate of lime. 



I may observe that I have carefully examined the shell-sand 

 from Bude for phosphoric acid, but have not succeeded in de- 

 tecting the least trace of phosphoric acid in this species of shell- 

 sand. 



This negative result, however, must not be taken as a proof 

 that shell-sand is invariably destitute of phosphoric acid. This 

 is not the case, for I have experienced no difficulty in recognising 

 distinctly the presence of phosphoric acid in several other kinds 

 of shell-sand, but with the exception of the sea-sand from Padstow 

 the proportions of this acid were too small to admit of a quantitive 

 determination. 



In the far-famed shell-sand from Padstow, on the other hand, 

 I found an appreciable quantity of phosphate of lime, as well 

 as a considerable quantity of sulphate of lime, both which con- 

 stituents it need hardly be mentioned add considerably to the 

 fertilizing properties of this species of shell-sand. 



A careful analysis of a sample of shell-sand kindly supplied 

 to me by Mr. Bryant of Padstow yielded the following results : 



Composition of Shell- sand from Padstow. 



Water and a little organic matter 1*233 



Oxides of iron and alumina 1*686 



Phosphoric acid -228 



(equal to bone-earth) . . . . ( *491) 



Carbonate of lime 80*080 



,, magnesia 3*176 



Sulphate of lime 1*049 



Chloride of sodium (common salt) .. ..' '314 



Insoluble silicious sand 12*127 



99*811 



This analysis fully establishes the superiority of the Padstow 

 sand over many other Cornish and Devonshire shell- sands, and 

 shows that 1 ton of one kind of sand may be worth to the farmer 

 as much and more than 4 or 5 tons of another locality. 



The amount of phosphoric acid in the Padstow shell- sand 

 analysed in my laboratory corresponds to about per cent, of 

 bone-earth ; and considering the large quantities of shell-sand 

 that are often laid on the land, besides much carbonate of lime, 

 an amount of bone-material will be added to it which cannot fail 

 beneficially to affect the crops raised on soils that have received a 

 good dressing of Padstow shell-sand. 



