110 PHILOSOPHICAL TRANSACTIONS. [aNN0 1791- 



drjj to dissolve readily in this alkali, but while still moist to do so very copiously, 

 even without the assistance of heat; and some of this solution, thus saturated 

 with siliceous matter by ebullition, being exposed to the air in a shallow glass, 

 became a jelly by the next day, and the day after dried, and cracked, &c. exactly 

 like the mixtures § 9 (d and e). And another portion of this solution mixed 

 with marine acid afforded no precipitate, and remained perfectly unaffected for 2 

 days ; but on the 3d it was converted into a firm jelly like that § Q (f). 



As gypsum is found to melt per se at the blow-pipe, though refractory to the 

 strongest heat that can be made in a furnace, it was thought that possibly silice- 

 ous and calcareous eartiis might flux together by this means, though they resist 

 the utmost power of common fires ; but experiment showed, that in this respect 

 quartz did not agree with tabasheer. But this difference seems much too likely 

 to depend on the admixture of a little foreign matter in the latter body, to admit 

 of its being made the grounds for considering it as a new substance, in opposition 

 to so many more material points in which it agrees with silex. Nor can much 

 weight be laid on the inferior specific gravity of a body so very porous. The in- 

 fusibility of the mixture § 13 (g) depended also, probably, either on an inaccuracy 

 in the proportions of the earths to each other, or on a deficiency of heat. 



3. Of the 3 bamboos which were not split before the r. s. Mr. M. opened 2. 

 The tabasheer found in them agreed entirely in its properties with that of N° 1 

 and 2. It was observed, that all the tabasheer in the same joint was exactly of 

 the same appearance. In one joint it was all similar to the yellowish sort N'^ 1. 

 In another joint of the same bamboo, it resembled the variety (c) of N° 2. Pro- 

 bably therefore the parcels from Dr. Russell, containing each several varieties 

 of this substance, arose from the produce of many joints having been mixed to- 

 gether. 



4. The ashes obtained by burning the bamboo, boiled in marine acid, left a 

 very large quantity of a whitish insoluble powder, which, fused at the blow-pipe 

 with soda, eflTervesced, and formed a transparent glass. Only the middle part of 

 the joints was burned, the knots were sawed off", lest, being porous, tabasheer 

 might be mechanically lodged in them. However, the great quantity of this re- 

 maining substance shows 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 fore- 

 going case. 



5. Since the above experiments were made, a singular circumstance has pre- 

 sented itself. A green bamboo, cut in the hot-house of Dr. Pitcairn, at Isling- 

 ton, 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 



