SPECIMENS OF SIR J. IIALl's EXPERIMENTS, 317 



ft is m a shining and almost transparent state ; at one end the Specimens of 

 flat form and the letter are still visible ; the other end is com- Spi^ed^o''^'^ 

 pletely rounded in fusion, with a glassy surface. strong heat 



Number 25, shews the substance produced by the combina- ^ioi,"by°Sir^'° 

 tion of carbonate of lime with pure silex. Part of the porcelain James Hall, 

 tube in this specimen is filled with pounded silex ; which having 

 a very feeble ags,luiination,is supported by some sealing-wax. 

 Upon the silex, during the experiment, had lain some carbonate 

 of lirne, the lower part of which had united with the silex, 

 producing a semitransparent substance, with a delicate tinge of 

 blue. The termination of this compound, as it had advanced 

 downwards into the silex, shews the rouad and mammillated 

 form of chalcedony. 



Number 26, result of an experiment with heat and com?- 

 pression, made July 22, 1805, with some pure carbonate of 

 lime, prepared by Mr. Hatchett. The carbonate was enclosed 

 in a small tube of platina, and was thus secured against all 

 contamination. 



Number 27, result of an experiment made likewise in platina, 

 with a fragment of a perriw inkle- shell : the form of the shell is 

 gtill visible, though the substance is glazed by semifusion. 

 ^long with it, on the same stand, is a small drop like a pearl, 

 formed by the intire fusion of one of the fragments ; and a 

 portion of a shell of the same kind, in its natural st^te, is in- 

 troduced, in order to show what change had taken place during 

 the experiment. 



Number 28, is a specimen of coal produced ft-om horn ; it is 

 a shining black substance, exactly resembhng pitch, or black 

 gealing-wax : it was formed in a low red-heat, and- in circum- 

 stances of compression ; by which, while some of the volatile 

 parts of the original were allowed to separate, others werfe 

 j-etained. It has thus acquired a jet-black colour, while it 

 retains its inflammability, and burns with bright flame. 



J^umber 29, likewise produced from an animal substance, 

 flannel. In this case, none of the compound parts of the 

 wiginal substance seem to have separated from it, owing either 

 to Jess heat or greater closeness, than in the last case. The 

 consequence has been, that the original colour has undergone 

 much less change, being of a yellow-red. At the same time 

 the substance has been in a state of fusion, and has assumed a 



polish 



