PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 301 
At Dalnabo it seems occasionally to pass into idocrase, which, with many 
other species, is abundant here; the garnets occur towards the more central 
and purer portions of the limestone bed. 
1-5 grammes yielded— 

Silica, : ; my oe 
From Alumina, . Peels 
"589 = 39 + 266 
Alumina, . 4 : s  2L.*976 
Ferric Oxide, . , + ers 7 
Ferrous Oxide, . 5 POL OS 
Manganous Oxide, . : 333 
Lime, : : : Ey refs 
Magnesia, . é ‘ : "6 
Soda, : : A - tr. 
Water, . j F ‘ *184 
99° 661 
6:281 per cent. of the silica was insoluble ; possible impurity unknown. 
As far as colour is concerned, this cinnamonstone is superior to the mineral 
obtained from Ceylon ; it is; however, so much flawed that it is useless for 
purposes of jewellery. 
In connection with the very common occurrence of garnets in limestone the 
question arises—can any explanation thereof be suggested ? 
In venturing upon an explanation, there are three facts upon which I have 
to found. 
The first: That the localities in which garnets are found to occur in lime- 
stone are—as regards the occurrence of silicates generally—the most richly 
mineral-bearing of any in the country. 
The second : That close observation of limestone strata among the metamor- 
phic rocks of the Highlands of Scotland shows that these limestones function 
in a manner somewhat similar to that of igneous rocks—I mean as regards the 
changes they induce, or seem to induce in the including rocks. 
The third: That this special mode of functioning—at first sight very 
anomalous as regards a substance and structure of unquestionable organic 
_ origin—is only to be observed in certain circumstances. 
If the limestone bed is thin, whether disturbed or undisturbed—convoluted 
or not so—there is no change. The stratum itself is still /imestone, a more or 
less impalpable paste, amorphous in its nature, structureless ; or if with recog- 
nisable structure, then it is that of an imbedded and badly developed organism. 

