46 I Capt. W. A. Ross on Pyrology, or Fire Analysis. [June 20, 



rate, the so-called "pure oxide of cerium" is thus shown, by one simple 

 operation, to consist in reality of no less than four substances. 



Lime, Strontia, Baryta, Alumina, Silica, and Magnesia. 



65. Of the alkaline earths, lime, as above mentioned, causes immediate 

 turbidity over the whole bead, and when added in greater proportion, pro- 

 duces round spots suspended in the turbid mass. These spots are perfectly 

 clear and colourless like drops of limpid oil in milk. When added in 

 very large proportion, the clear spots collect in one large one, which, if 

 still further addition of lime is made, absorbs the remainder of the turbid 

 part, leaving the whole bead beautifully clear and colourless. The turbid 

 part, therefore, would appear to be an attempted solution of the lime by the 

 boric acid ; the clear part, a complete solution of the boric acid in the borate 

 of lime. 



66. Strontia forms large beautiful vitreous-looking globules, quite trans- 

 parent and even refractive ; they have great specific gravity, and can be 

 easily aggregated at the bottom of the bead. Baryta affords sphericles like 

 fish-eyes, transparent at first, but soon becoming opaque. Magnesia is not 

 at first acted on byB, but after a short O. P. resolves itself into opaque, 

 white, and compact sphericles like miniature snow-balls ; these, after 

 long O. P., and consequent exhaustion of B, are clarified and become 

 transparent, but are again rendered opaque by the addition of fresh B. It is 

 concluded from this fact that these contained balls have a fixed relative 

 proportion as regards quantity to the containing B. Alumina and silica 

 remain as amorphous fragments, and do not congest into globules ; those 

 of the former are white and opaque like pieces of fat ; of the latter semi- 

 transparent. 



The Alkalies. 



C7. Soda, potash, and lithia appear to be the only substances which 

 dissolve completely in boric acid in any proportion, and hence the value of 

 the latter as a detective agent for them, and also as an alkalimeter ; for if a 

 very small trace of soda or potash contained in a mineral or salt be applied 

 to a B bead having globules of cobalt (for instance) suspended in it, those 

 nearest the side where the alkali is applied are dispersed and spread over 

 that side as a pink suffusion. If 5 per cent, be added, the sphericles of 

 cobalt disappear, the whole bead is clarified, and assumes a blue colour 

 while hot, but remains pink on cooling. If 17 per cent, be added, the bead 

 remains blue on cooling, and (in the case of soda) borax has been formed ; 

 but this method would probably be considered incomplete if it did not 

 afford a means of distinguishing between, as well as of measuring these two 

 alkalies ; and this it does as follows : — 



Vesiculation. 



68. If the B bead, on the addition to it of the substance to be examined, 

 shows, by the reaction above described, that an alkali is contained in the 



