384. Clarke and Diller—Topaz from Stoneham, Me. 
Two other derivatives of this group of compounds may be 
cited for example of an extension of this process, namely, 
westanite (or woerthite, a hydrous fibrolite) and kaolin. I 
half of the water in the latter mineral be regarded as water of 
crystallization, the formula of kaolin will become that of 
xenolite with an aluminum atom replaced by three atoms of 
hydrogen; but if all the water be regarded as combined, the 
statement takes the following graphic form: 
SiO =Al H 
Al—Si0.=Al Al—Si0,=Al Al—sSiO,—H, 
“SiO = “SiO ,=Al “SiO, =A 
Xenolite. Westanite Kaoli 
The suggestiveness of such formule can hardly be questioned, 
and a close examination of them will show that they also fulfill 
the main purpose of structural formule; namely, that they 
indicate probable lines for fruitful synthetic research. 
One more question may be included within the scope of the 
present paper. What has become of the fluorine withdrawn 
colorless on heating. 
pO SSS sara AONE aie ca iaeaie Sol aaa ee 47°60 
1S ESE a ele ee ~ 08 
RN ee 1°44 
kw cae 40°36 
ee eS 0°29 
a a 6°84 
RE NG Oe a ena 0711 
102°72 
Deduct oxygen................ 2°94 
99°78 
The high proportion of fluorine found in this analysis W% 
undoubtedly due to intermixed fluorite. The large amount ¢ 
esla, moreover, suggests the desirability of a careful sear’ 
at the locality for wagnerite, 
In conclusion, w st express our indebtedness t? et 
Whitfield for the care and thoroughness with which he exec4 
the troublesome analyses, 
