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



Before offering any remarks on these analyses, I give the com- 

 position of another sample of shell-sand from Bude, which was 

 collected a year after the first sample. The following analysis 

 of Bude sand therefore is calculated to show the variations in 

 composition to which this sand is subject at different times. 

 Grouped together with this analysis is another, made in my labo- 

 ratory, of a sea-sand from Sandymouth, Cornwall. 



Composition of a second sample of Shell-sand from Bude (No. I.), and 

 Sea-sand from Sandymouth, Cornwall (No. II.) 



No. I No. II. 



Water and a little organic matter . . . . 2'52 . 3'51 



Oxides of iron and alumina . 8*50 



Carbonate of lime 52*59 



magnesia '98 



Silicious sand 35'33 



Chloride of sodium (common salt) . . . . '38 



3-48 

 43'27 



1-70 

 48-29 

 not determined 



100-30 .. .. 100-25 



On comparing these analytical results with each other it will 

 appear: 



1. That the proportions of carbonate of lime in the analysed 

 samples of sea-sand from different localities vary exceedingly. 

 Thus, whilst the sand from Comb Martin contained only 14 per 

 cent., that from Northcote Mouth and that from Summerliege 

 contained 62i and 63 per cent, respectively. 



2. That the samples richest in lime contain least silicious 

 sand, and those poorest in lime the most silicious matter. 



3. That the proportion of oxide of iron likewise varies con- 

 siderably in the sands from different places, which circumstance 

 no doubt explains at least to some extent the various colours of 

 the different kinds of sea-sand analysed by me. 



4. That the proportion of soluble alkaline salts in all samples 

 is very trifling. 



5. That the specimen of sea-sand from Comb Martin examined 

 in my laboratory is too poor in lime to be profitably carried 

 away any distance. 



6. That the sea-sands from Northcote Mouth and Summerliege 

 possess nearly the same agricultural value, and are the best varie- 

 ties of the samples of sand the composition of which is stated 

 above. 



7. That Bude sea-sand varies but little as regards the propor- 

 tion of carbonate of lime which different samples drawn at long 

 intervals contain. 



8. That Bude sand contains rather more than one half its 

 weight of carbonate of lime, and the shell-sand from Sandymouth 



