Dec. 1, 1864.] THE TECHNOLOGIST. 



GUM-RESINS OF VICTORIA. 229 



gums are less soluble than the gum arabic of commerce ; but, on the 

 other hand, they appear to yield a more adhesive mucilage, which is less 

 .liable to splinter and crack when dry. Most of these bodies possess a 

 slight amount of astringency, which varies in one and the same sample 

 from a single tree ; and it would seem that while this peculiarity is ab- 

 sent, or but very faintly perceptible, in the pale-coloured pieces, it in- 

 creases in proportion as the colour of the gum deepens — a circumstance 

 which would much facilitate their classification. 



Under the term Gum-Eesins, a numerous series of indigenous vege- 

 table productions may be classed which could be procured in great 

 abundance in Victorian-tut which have not hitherto received the atten- 

 tion they deserve. They are produced in greater or lesser quantities by 

 all the species of the genus Eucalyptus, and might be largely accumu- 

 lated with little trouble by wood-splitters and sawyers throughout the 

 forests of the country. 



These substances occur within the trunks of trees of all sizes, in 

 flattened cavities in the otherwise solid wood, which often lie parallel 

 to the rings of growth. In such places the deposition of gum, which is 

 at first a viscid liquid, becomes gradually inspissated, and subsequently 

 hard and brittle. The liquid gum may also be obtained by suitable in- 

 cisions in the stems of growing trees ; but whether such a method affords 

 greater facilities for its collection than those naturally offered, appears 

 to be still an undecided question. 



In their general characteristics the gum-resins from the Eucalypti 

 resemble each other very closely. When in the solid form they present 

 the appearance of small angular masses, intermixed with occasional 

 striated pieces and particles of wood. The prevailing colour is dark 

 red-brown, in some cases dull with olive and yellowish tints, in others 

 bright ruby-coloured and transparent ; black and opaque pieces are also 

 very commonly found interspersed through each of the several descrip- 

 tions of gum-resin. 



The fracture, when these substances are thoroughly dried in the 

 water-bath, is vitreous, and they are, moreover, then exceedingly friable, 

 and easily pulverized. Dessication in this way causes them to lose from 

 fifteen to twenty per cent, of their weight. 



In the mouth they are tough and adhere to the teeth, colouring the 

 saliva red ; their taste is intensely astringent, without much bitterness ; 

 although it should be remarked that in this particular they are not all 

 equally potent. 



The liquid gum-resins are very viscid treacle-like fluids, which do 

 not differ in chemical constitution from those which have undergone 

 induration, save that they contain about sixty-five per cent, of water, 

 capable of being expelled by the temperature of a water-bath. 



The solvent action of water on these bodies is not the same in the 

 case of gums from different species of trees. If, for instance, cold water 

 be poured on the produce of the F. corymbosa, whether it be in the solid 



