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



appeared to me not unlikely that the agricultural value of different 

 kinds of lime might be influenced by the relative proportions of 

 phosphoric and sulphuric acid which they contain. In order 

 to ascertain if the best agricultural limestones really contain 

 more phosphoric acid than others less valued by the farmer, I 

 procured several kinds of limestones, and submitted them to 

 a refined process of analysis, in which especial care was taken to 

 ascertain accurately the amount of phosphoric acid. 



The results of this examination are embodied in the subjoined 

 Table : 



Composition of Carboniferous, or Mountain Limestone, from Williamson, 

 Pembrokeshire (No. I.); Mountain Limestone from Ashburton, Devon- 

 shire (No. II.) ; and Silurian Limestone from Llandew, Pembrokeshire 

 (No. III.). 



No. I. 



050) 

 170J - 



718 

 012 



. ( -026) 

 ..: -100 

 . 1-490 

 1-760 



Moisture 



Water of combination 

 Oxides of iron and alumina 

 Phosphoric acid 

 Equal to bone-earth . . 

 Sulphate of lime . . 2. -' 



Magnesia 



Insoluble silicious matter 

 Carbonate of lime 



No. II. 



200 



100-200 



95-490 

 99-770 



No. UL 



rl20 

 {230 



683 

 077 

 ( -166) 

 050 

 150 

 13-720 

 84-740 



99-810 



On comparing these analytical results with each other it will 

 be seen : 



1. That the proportion of phosphoric acid in the less pure 

 Silurian limestone from Llandewi is somewhat greater than in 

 the much purer limestones from Williamson and Ashburton, 

 and that in all three limestones the quantity of phosphoric acid 

 is very small. 



2. That the proportion of sulphate of lime or gypsum likewise 

 is very inconsiderable in all three specimens analysed. 



3. That No. III. contains nearly 14 per cent, of insoluble 

 silicious matter, whilst No. I. contains a mere trace, and No. II. 

 not quite 2 per cent. 



4. That the proportion of pure carbonate of lime is very 

 large in the limestone from Williamson, somewhat smaller in 

 the Ashburton limestone, and considerably smaller in the Llan- 

 dewi stone. 



5. That No. I. altogether contains only 1 per cent, of foreign 

 matters, whilst in No. II. there are 4j per cent, and in No. III. 

 about 15 per cent, of foreign matters. 



6. That the amount of magnesia found in either of these three 

 limestones is inconsiderable. 



