LEGUMINOSJE. 333 



hard, and towards the centre dark, and is so heavy as to sink 

 in water. It has a sweetish astringent taste, but little or no 

 smell. Infused in water or alcohol it gives out at first a fine 

 red colour with a shade of purple ; but as the process is con- 

 tinued, it becomes gradually deeper, and at last almost black. 



According to Chevreul, Logwood contains a volatile oil, tan- 

 nin, a yellow colouring matter, and acetates'of lime and potash. 

 But the most remarkable of its constituents is the newly dis- 

 covered substance to which the name of Hematin has been 

 given. It was obtained by Chevreul by evaporating the fil- 

 tered watery infusion to dryness ; digesting the residue in alco- 

 hol, which on being again filtered and evaporated yielded crys- 

 tals of Hematin of a reddish white colour. This principle is 

 supposed to constitute the colouring matter of Logwood. 



The principal consumption of Logwood is in dyeing. When 

 of a good quality it yields from T 'j to ^L of pure colouring mat- 

 ter. No colouring substance affords so great a variety of dyes. 

 Chips of it boiled in water acidulated with sulphuric acid afford 

 a brownish yellow decoction, which communicates to wool a 

 bright snuff colour of considerable durability. If nitric acid 

 be substituted, the infusion becomes a bright yellow ; and if 

 muriatic acid, a brownish yellow. Alum throws down a pur- 

 ple or reddish violet precipitate ; sulphate of iron, a copious 

 bluish black ; sulphate of copper, a purplish blue ; the solutions 

 of tin, purple or violet ; sulphate of pure zinc, a dark purple ; 

 muriate of antimony, a beautiful crimson ; acetate of lead, a 

 black precipitate with a slight reddish tinge ; muriate of barytes, 

 a reddish purple ; sulphate of lime, a purple ; arseniate of pot- 

 ash, a deep yellow. 



The salts of tin as mordants give the best and most perma- 

 nent of the purple or violet colours obtained from Logwood, 

 and the sulphate of copper or verdigris, a blue of little bright- 

 ness or permanency, but recommended by its cheapness. 



Logwood is principally employed in dyeing, to give a lustre 

 and velvety cast to blacks, and for greys of certain shades. It 

 also affords certain compound colours which it would be difficult 

 to obtain of equal beauty and variety from colouring matters of 

 a more permanent nature. The great disadvantage indeed of 

 the dyes obtained from Logwood is their want of permanency. 



I need scarcely add that the infusion of Logwood is an im- 

 portant material in ink-making. 



The wood of this tree, from its great hardness and compact- 

 ness, takes a fine polish. I am not aware that it has as yet 

 come into use among our Cabinet-makers. 



The tree itself makes a beautiful and strong fence. It is 

 usually established by means of young plants, which may be pro- 

 cured in great abundance wherever the old trees grow. They 

 should be all of nearly the same size and strength, and they ought 

 to remain untouched by the pruning-knife till the end of the 



