124 Chronicles of Science. [Jan. 
sedimentary strata have been rendered crystalline by metamorphism, 
their future alterability becomes difficult, because their permeability to 
water is so enormously diminished, and it is not until they are once 
more broken down to the condition of soils and sediments, that they 
become again subjected to such important chemical changes as we 
have described. Hence, the mean proportions of alkali and alumina 
in the composition of the clay sediments of any geological period will 
depend not only upon the age of the formation, but upon the number 
of times its materials have been broken up, and the periods during 
which they have remained unmetamorphosed and exposed to the 
action of infiltrating waters. Such are the general principles which 
in this excellent paper Mr. Hunt brings to bear upon the actual state 
of the metamorphic rocks of Canada from the Carboniferous to the 
Lower Silurian, and down to the azoic rocks and granite, even the 
veins of which he regards as formed like metalliferous veins by 
aqueous deposition in fissures. 
The Sixth Annual Report of the Maine Board of Agriculture* 
recently circulated, presents a feature not so common in this country 
as it deservedly ought to be, an association of geological investigations 
with the practical pursuit of agriculture. Even in the first few pages 
on the application of fish-manure, and where we should have little 
expected it, we find practical hints from the geologist. Commenting 
on Mr. Bruce’s endeavour to introduce this to us very objectionable 
and disgraceful appropriation of the most extensive source of animal 
food which nature supplies to mankind, Mr. Sterry Hunt recommends 
the combination of the fish-manure with calcined shale for the pur- 
pose of driving away insects from the plants to which it is applied. 
Distilling a black bituminous shale from Port Daniel at a red heat, 
the disengaged vapours were passed through a vat containing the fish, 
which by the continuance of the heat were ultimately reduced to a 
pulpy mass. The calcined shale, ground to powder, was mingled 
with this; the whole being then dried. Experiments made with 
the manure are reported to have given satisfactory results ; it might 
be well if English agriculturists should pay some attention to the 
poorer kinds of bituminous shales which are met with in the British 
Isles, and even the refuse of the richer sorts, such as the Kimmeridge 
and the Glasgow shales, which have been used for making gas, might 
be in this way turned to a useful and profitable account, not necessa- 
rily for mixing with fish-manure, the use of which we have strongly 
deprecated, but for commingling with many other classes of manures, 
as the chief efficacy calcined shale possesses against noxious insects 
appears to be in the presence, or perhaps in the odour, of the bitu- 
men it contains; for it is known that coal-tar applied to the in- 
terior wood-work in greenhouses has the effect of expelling those 
unwelcome intruders. Such bituminous sandstones as those of Caith- 
ness, might thus be turned to profitable account, and there are other 
* «Sixth Annual Report of the Secretary of the Maine Board of Agriculture.’ 
Augusta: Stevens and Hayward, 1861-2. 
