v.] THE LIME IN THE MORTAR. 115 



acid from the air and water, enough to harden it again 

 into limestone : and that it will take some time in 

 doing. A thick wall, I am informed, requires several 

 years before it is set throughout, and has acquired its 

 full hardness, or rather toughness ; and good mortar, 

 as is well known, will acquire extreme hardness with 

 age, probably from the very same cause that it did 

 when it was limestone in the earth. For, as a general 

 rule, the more ancient the strata is in which the lime- 

 Btone is found, the harder the limestone is ; except in 

 cases where volcanic action and earthquake pressure 

 have hardened limestone in more recent strata, as in 

 the case of the white marbles of Carrara in Italy, 

 which are of the age of our Oolites, that is, of the 

 freestone of Bath, etc., hardened by the heat of 

 intruded volcanic rocks. 



Bat now: what is the limestone? and how did it get 

 where it is not into the mortar, I mean, but into the 

 limestone quarry ? Let me tell you, or rather, help 

 you to tell yourselves, by leading you, as before, from 

 the known to the unknown. Let me lead you to 

 places unknown indeed to most; but there may be 

 sailors or soldiers among my readers who know them 

 far better than I do. Let me lead you, in fancy, to 

 some island in the Tropic seas. After all, I am not 

 leading you as far away as you fancy by several 

 thousand miles, as you will see, I trust, ere I have 

 done. 



Let me take you to some island : what shall it be 

 like ? Shall it be a high island, with cliff piled on 

 cliff, and peak on peak, all rich with mighty forests, 

 like a furred mantle of green velvet, mounting up and 

 ap till it is lost among white clouds above ? Or shall it 



i 2 



