456  Oross and Hillebrand—Minerals im the basalt of 
bundles arranged ina loosely and irregularly radiate manner 
form bunches an inch or more in diameter, upon which the 
delicate needles of mesolite have a special tendenc cy to deposit 
themselves. Reference will be made to this again later. 
the following chemical analyses, that under I is of the 
older, and that under IT of the more recent growth. In eac 
case the percentages under 6 denote repeated determinations. 
The material for I was carefully selected with a view to purity. 
The imperfectly spherical aggregates were broken up quite 
article appropriated for analysis was first 
possible. ad comparatively few of 
them, and the increased percentage of SiO, probably indicates 
the amount of the impurity teat 
i IL. eas IV. 
a b. a b 
| 
Si0,....| 40°681 40-703 42-662 | 41:6 40°877 
Al,Os...| 307117 | 29-749 29-252 29-286 |. , 
CaO ....|  11°921 | 11-895 10-900 10-900 
Na,O...| 4444 | 4°920 
H.0 12°857 12275 12,337 
100-020 | 100-009 | 
From the above figures, the following oxygen ratios are 
obtained : 
RO : AlO, : SiO, : H,O 
B; 1 BO a TE Us 261 
Il. 1 OO se OLY oe 2-248 
These ratios agree quite well with those in the variety for- 
oe called mesole or fardelite. But that thomsonite which 
to be cumaenn by Dana, Rammelsberg, Naumann- 
Zirkel a others, has a ratio of about 1:3:4:24, and Dana* 
bare Laeger that the high percentage of silica in mesole, 
is due to an admixture of quartz, aa gi etc. Thinking it 
barely saaatia that some sh escaped notice in ob- 
taining material for I, thus increasing the percentage of silica, 
a second portion of thomsonite from e same specimen ab 
* A System of Wisiesleny. ed, of 1874, p. 424. 
