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



It follows from these analytical results that the Williamson 

 limestone, notwithstanding the somewat smaller amount of phos- 

 phoric acid in comparison with No. III., is by far the best, and 

 has to be considered as one of the most valuable agricultural 

 limestones that can be found anywhere. This limestone indeed 

 contains nearly as much pure carbonate of lime as the Carrara 

 marble, the composition of which is stated by Wittstein, who 

 analysed it, as follows : 



Composition of Carrara Marble. 



Carbonate of lime 99' 236 



magnesia 



Oxide of iron '251 



Silica none 



99-771 



On burning, the limestone from Williamson yields a splendid 

 white lime, which readily slakes spontaneously on exposure to 

 the air, and falls to a light powder as fine as flour. 



The Ashburton limestone, though not quite as good as the 

 limestone from Williamson, is an excellent agricultural lime- 

 stone. It burns well, and also falls to a fine white and light 

 powder. This Silurian limestone, on the contrary, like the other 

 Silurian limestone the analysis of which has been stated already, 

 and indeed like most Silurian limes tones, does not produce a very 

 good lime. 



The limestone from Llandewi, I am informed by Mr. Morgan 

 of Haverford-West, who supplied me with most specimens of 

 Welsh limestones, makes a red-coloured lime, which by some 

 farmers, on account of its somewhat cheaper price, is preferred to 

 the beautifully white and extremely light lime from Williamson. 

 I believe, however, that it is bad economy to save a few shillings 

 in the purchase of an inferior lime, if such a splendid lime as 

 the Williamson lime can be easily obtained at a trifling higher 

 price. 



Oolitic limestones. These are very common in Gloucester- 

 shire and part of Somersetshire. The best lime of the oolitic 

 limestone series is produced from the Great Oolite or Bath 

 stone. 



Limestones belonging to the Inferior Oolite rock are invariably 

 of less value for lime-burning than the Great Oolite rocks. 

 Cornbrash, Forest Marble limestone, and Stonesfield slate, a 

 variety of slaty limestone, I believe are seldom, if ever, used 

 for the making of quicklime. 



I shall first notice the composition of Great Oolite and Inferior 

 Oolite limestone, and then give in a separate Table the composi- 

 tion of the other oolitic limestone rocks. 



