VOL. LXXXIV.] PHILOSOPHICAL TRANSACTIONS. 437 



many of their combinations are so very different in the 2 cases, as to determine 

 white lac and bees-wax to be different species of substances, though they agree 

 with each other in more properties than they do with any other known bodies. 

 As to the pe-la of the Chinese, we cannot judge of it unless a more particular 

 account had been given of its qualities. 



4. White lac and bees-wax appear to be homogeneous substances, and to con- 

 sist of the same kind of constituent parts, but the proportion of these parts is 

 very different in the two substances ; and hence the difference in the properties 

 of bees-wax and white lac. I consider the phosphate of lime, the soda, and mu- 

 riate of soda, as extraneous to the composition of lac. The different compo- 

 sition of the 1 substances may enable us to explain in a probable manner the 

 different action of other bodies on them. For instance, as it appears that a 

 much greater proportion of carbon enters into the composition of white lac than 

 bees-wax, the quantity of oxygen gaz in atmospheric air, applied under the usual 

 circumstances of combustion, is not sufficient to combine with the whole of the 

 carbon and other components of a given part of white lac, therefore a portion 

 of carbon remains uncombined in the form of soot, or a sublimate ; but when 

 oxygen gaz is applied, the whole of the carbon is combined with it, and of course 

 no smoke appears. The smaller proportion of carbon in bees-wax than white 

 lac, affords a probable reason why there is less smoke during the combustion of 

 bees-wax than white lac. It appears reasonable to conclude, that white lac might 

 be made to serve for illumination and combustion as well as bees-wax, either by 

 diminishing the proportion of carbon, or by increasing the proportion of the 

 other components ; but my knowledge of chemistry does not enable me to effect 

 either of these changes. 



XXII. Account of some Remarkable Caves in the Principality of Bayreuth, and 

 of the Fossil Bones found there. Extracted from a Paper sent, with Specimens 

 of the Bones, as a Present to the Royal Society, by his most Serene Highness 

 the Margrave of Anspach, &c. p. 402. 



A ridge of primeval mountains runs almost through Germany, in a direction 

 "^nearly from west to east ; the Harlz, the mountains of Thuringia, the Fichtel- 

 berg in Franconia, are different parts of it, which in their farther extent consti- 

 tute the Riesenberg, and join the Carpathian mountains ; the highest parts of 

 this ridge are granite, and are flanked by alluvial and stratified mountains, con- 

 sisting chiefly of limestone, marl, and sandstone ; such at least is the tract of 

 hills in which the caves to be spoken of are situated, and over these hills the 

 main road leads from Bayreuth to Erlang, or Nurenberg. Half way to this 

 town lies Streitberg, where there is a post, and but 3 or 4 English miles distant 

 from thence are the caves mentioned, near Gailenreuth and Klausstein, two 



