On the Phosphoric Strata of the Chalk Formation. 
83 
in which thej are imbedded. They were analysed, with the fol- 
lowing results* : — 
OUillUiC (iliu lliaLfiUUlc oJiiLiUiio ill a. I Id 
1 9, 
• 1 0 
• 53 
Wii tor 
vV aLLl • • • . . 
O 
•19, 
X llUbli IJUl \\j uClU • • • • 
90 
65 
Carbonic acid .... 
4 
01 
Sulphuric acid .... 
5 
13 
Lime ..... 
. 34 
61 
Oxide of iron .... 
7 
24 
Alumina ..... 
98 
Potash ..... 
1 
79 
Soda ..... 
1 
87 
97-09 
* These green grains are very interesting : from their form and colour, in both 
of which respects they closely resemble the green particles of the true " gi'een- 
sand," it is impossible to resist the impression that their formation is in 
some way connected w ith these latter. By way of comparison a partial analysis 
was made of some of the small green grains, picked grain by grain from a 
speckled marl before mentioned. The results were as follows : — 
Insoluble siliclous matter . . . .45*02 
Pliosplioric acid . . • . . .5*71 
Lime ....... 13*16 
Oxide of iron . . . . . .13*42 
Here too it would seem that these green grains may contain a considerable per- 
centage of phosphoric acid. 
Such is not, however, always or necessarily the case, for in several instances 
the very greenest specimens have been examined for phosphoric acid, and 
have been found to contain scarcely any ; thus an exceedingly green sand from 
Chard contained only * 069 per cent, of phosphoric acid, equal to * 142 per cent, 
of bone-earth. It is certainly not quite clear that the green grains may not have 
originally contained phosphoric acid in all cases, for it is observed that wher- 
ever this ingredient is wanting the grains have a lighter colour and a less 
compact structure, and are often broken up into a finely comminuted green 
powder, which will remain for many hours suspended in water. This effect 
may be due to a weathering, in the course of which the phosphoric acid is 
more or less removed, and it may be produced artificially by digesting the 
grains in dilute hydrochloric acid, which readily removes the phosphate of 
lime without destroying their form. 
The same remarks apply to the different results which have been obtained 
by various chemists in regard to potash as an ingredient of the green-sand. 
In some cases only traces of this alkali have been detected — in others as much 
as 10 or riper cent, has been found. It must be borne in mind that what is 
usually called <jrecn sand" is a variable mixture of green grains with pure 
white particles of quartz, and that the latter form by far the largest projjortion 
— the green colour of the real particles being so intense as to exhibit itself 
when largely diluted. 
In the green-sand from Chard just described, the following quantities of the 
alkalies were found : — 
Potash 0 129 per cent. 
Soda ....... 0*121 ])er cent. 
— the sand being fused with barytes. 
G 2 
