438 VEGETABLE SUBSTANCES. 



us, that the naked hillocks of Mount Ida in Candia 

 produce this plant abundantly. The gum exudes 

 spontaneously towards the end of June and in the 

 following months, during which period the nutritious 

 juice of the plant, thickened by the summer heat, 

 bursts most of the vessels in which it is confined. 

 This juice coagulates in threads, which make their 

 way into the pores of the bark, through which being 

 pushed forward by fresh juice they issue forth, and 

 are at length hardened in the air, either in irregular 

 lumps, or in long vermicular pieces bent into a 

 variety of shapes *. The best sort is white and semi- 

 transparent, dry, but somewhat soft to the touch. 

 It is extremely different in many of its properties to 

 gum arabic ; one part of this diffused in one hundred 

 parts of water affords a fluid of the same consistency 

 as one part of gum arabic dissolved in ten parts of 

 water. Water is, however, but an imperfect solvent 

 to it, not forming the same intimate union with it as 

 with other gums. When tragacanth is put into water 

 it slowly imbibes a great quantity, swells into a large 

 volume, and forms a soft, but not fluid mucilage. 

 On the addition of more water, and if the mixture be 

 agitated, the gum will be more generally diffused 

 throughout the liquor, which will appear turbid. If 

 left at rest the mucilage will again separate and 

 subside; the supernatant water appearing limpid, 

 and holding only a very small portion of the gum. 



This is more costly than gum arabic or Senegal, 

 but its employment is highly beneficial in topical 

 dyeing, when the mordant is prepared with nitrous 

 acid ; since other gummy solutions are coagulated by 

 the application of this active alterative. 



In 1830 the quantity of tragacanth retained for 

 home consumption was 29,725 Ibs. It is admitted 

 on a duty of Is. per Ib. ; its price being from 16 to 

 18 per cwt. 



* Voyage Du Levant, torn. i. p. 64. 



