WRITINGS OF JAMES SMITHSON. 17 



substance shews it to be an essential, constituent part of 

 the wood. 



The ashes of common charcoal, digested in marine acid, 

 left in the same manner an insoluble residuum which fused 

 with soda with effervescence, and formed glass; but the 

 proportion of this matter to the ashes was greatly less than 

 in the foregoing case. 



5. Since the above experiments were made, a singular 

 circumstance has presented itself. A green bamboo, cut in 

 the hot-house of Dr. Pitcairn, at Islington, was judged to 

 contain Tabasheer in one of its joints, from a rattling noise 

 discoverable on shaking it; but being split by Sir Joseph 

 Banks, it was found to contain, not ordinary Tabasheer, but 

 a solid pebble, about the size of half a pea. 



Externally this pebble was of an irregular rounded form, 

 of a dark-brown or black colour. Internally it was reddish 

 brown, of a close dull texture, much like some martial sili- 

 ceous stones. In one corner there were shining particles, 

 which appeared to be crystals, but too minute to be distin- 

 guished even with the microscope. 



This substance was so hard as to cut glass I 



A fragment of it exposed to the blow-pipe on the char- 

 coal did not grow white, contract in size, melt, or undergo 

 any change. Put into borax it did not dissolve, but lost its 

 colour, and tinged the flux green. With soda it effervesced, 

 and formed a round bead of opaque black glass. 



These two beads, digested in some perfectly pure and 

 white marine acid, only partially dissolved, and tinged this 

 menstruum of a greenish yellow colour ; and from this so- 

 lution Prussite of tartar, so pure as not, under many hours, 

 to produce a blue colour with the above pure marine acid, 

 instantly threw down a very copious Prussian blue. 



P. S. — In ascertaining the specific gravity of the Ilydra- 

 bad Tabasheer, § I. (G), great care was taken in both the 

 experiments that every bit was thoroughly penetrated with 

 the water, and transparent to its very centre, before its 

 weight in the water was determined. 



