planes correspond with the planes of stratification, otherwise they cross the strata like cleavage planes. The rocks in which foliation exists are called schists. The term slate ought to be limited to those fissile rocks that are homogeneous, and schist to those where the materials are heterogeneous, and are arranged in alternate layers.

The following are those rocks which have been metamorphosed from sedimentary strata: Quartz Rock, Clay Slate, Mica Schist, Talcose Schist, Steatite, Serpentine, Hornblende, Gneiss and Saccharoid Azoic Limestone. Probably most of the Granitic group of unstratified rocks have been altered from Gneiss, Hornblende Schist and Talcose Schist.

Whenever therefore the geologist finds an Azoic rock the question immediately arises, What is the age of this rock? Is it Laurentian, Devonian or Carboniferous? There is comparatively little difficulty in determining the age of fossiliferous rocks on account of the fossils; but as fossils are wanting in the Azoic rocks some other course must be adopted. There are two ways of ascertaining the age of Azoic rocks. By one method the identity of an azoic with a fossiliferous rock may be determined by following one of them along the line of its strike until it passes into the other. By the other method we may determine the age of the azoic rock proximatively, by noting what formation lies beneath it and what formation lies above it. Azoic rocks have been found even in the Tertiary group.*

A large part of the rocks of Maine are metamorphic. They are doubtless all below the Coal Measures, but whether they are Devonian, Silurian, Cambrian or Laurentian, or all of them, is at present unknown. It will be a part of the work of the Scientific Survey to answer this question. Though the question appears purely a matter of curiosity, yet practical issues are dependent upon its decision. This leads us to speak of the

Utility of a Geological Survey.

In the first place, the geological survey of a State develops its

*Those who wish to learn more of the elements of geology than can be derived from this report are referred to our text-book on this subject-Elementary Geology, by Edward Hitchcock and Charles H. Hitchcock, for use in schools, families, and by individuals; Thirty-first Edition; published by Ivison, Phinney & Company of New York.

mineral wealth. Valuable mines of metals and quarries of useful and ornamental building stones are locked up in the solid rocks, which will remain in obscurity until developed by accident or systematic exploration. Modern science has found uses for many substances previously considered worthless. There are often connections between widely separated deposits of the same substance, which only an acquaintance with the earth's crust will discover. A strict examination of a State ought to develop its most important subterranean resources.

Facts show of how great advantage geological surveys have been. The help afforded to quarrymen and miners by the geological examination of such States as Vermont and Canada has more than repaid all the expenses of exploration. In a new country where settlements have never been made, the opportunity for developing new mineral resources is greater than in thickly populated districts.

In the second place, the geological survey of a State points out clearly those districts where no valuable mines or quarries can be worked. In our view this is the most important result of a scientific survey. There are very few towns in New England where some of the inhabitants do not believe that they live adjacent to rich subterranean treasures. An Indian has chopped off a piece of lead from a ledge and run it into bullets, or some one has been secretly treasuring up a few worthless minerals closely resembling the precious metals. Very often the reputed original discoverer has refused to disclose the locality of the valuable substance, yet its existence in large quantities is steadfastly believed. A systematic exploration can very easily eliminate the worthless from the valuable in all these and scores of similar cases, and forestall useless expenditure. It would surprise one not familiar with the subject to learn how numerous have been the outlays of capital in the vain search for valuable ores. Doubtless a volume could be filled with brief accounts of the losses sustained by the citizens of Maine alone in these unfortunate efforts. Probably a scientific exploration at the outset would have developed the true character of the localities, and saved many thousands of dollars, besides an immense amount of mortification and disgrace.

In the third place, the geological survey of a State furnishes a basis for intelligent agricultural operations. It furnishes data from which to judge of the character of the soil. By its aid the different

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soils of a State may be classified according to their relative values, and their respective areas be represented by colors upon a map. Such a map might lead farmers to select the best sites for their labors, particularly in moving into a new country. A thorough examination of the different soils may point out what materials ought to be added to make them more productive.

A geological survey aids the agricultural interest also by pointing out deposits of natural manures. Opportunities of this sort are generally quite abundant.

In the fourth place, the geological survey of a State diffuses much scientific information in that State, and encourages the study of the works of nature. The benefits resulting from the acquisition of theoretical knowledge are not generally reckoned in dollars and cents; still they have a pecuniary value. The liberalizing bias given to a young man by scientific knowledge may be a source of pleasure to him in later years, as well as prevent him from dissipation. The possession of this tendency is worth thousands of dollars to him. Would it not be financially desirable even to educate the scholars of the common schools in the general principles of the natural sciences? It can be established by statistics that wealth is the most abundant where there is the greatest amount of general information.

Rock formations in Maine.

The formations in Maine are both metamorphic and fossiliferous, the former predominating. The following metamorphic stratified rocks occur in Maine:

It is difficult as yet to say whether any of these Azoic rocks belong to the Laurentian series or the Paleozoic system. Scientific men are now discussing this very question in connection with some side issues, not confining their discussions by any means to Maine.

The following unstratified rocks are found in Maine. As to their ages the same may be said in general as was said respecting the

age of the Azoic stratified rocks. There are a few exceptions, which will be specified in the body of the report:

GRANITE,

SYENITE,

PROTOGINE,

PORPHYRY,

Trap or GreenNSTONE,
EURITE.

The fossiliferous rocks of Maine are all Paleozoic, except certain marine Alluvial deposits. They probably belong to the following.

From the observations we have made during the summer, and from Dr. Jackson's printed reports, we are enabled to construct a geological map of the whole State, representing upon it the different rocks by different colors. As this map is imperfect, it is deemed advisable to suspend its publication for the present; but a manuscript copy of it is presented with this report, so that in case the work of exploration should cease, the total results of all previous explorations will not be lost. Every year's work will make this representation more perfect. We proceed now to describe the character and distribution of the Azoic stratified rocks of the State.

GNEISS.

This rock is composed of successive folia of quartz, mica and feldspar. The constituents are the same as those of granite. As in granite the mica and the feldspar are generally the potash mica and the potash feldspar; especially in Maine. When gneiss contains crystals of feldspar which give it a spotted appearance, it is said to be porphyritic. It is granitic when it is difficult to distinguish it from granite. Hornblende and epidote are sometimes so abundant in gneiss as to give it a distinctive character, when it is called hornblendic and epidotic. Gneiss is often distinguished for the regularity and evenness of the stratification, by which it is rendered an excellent building stone.

The principal deposit of gneiss in Maine is near the coast, extending from Westbrook eastwardly across Penobscot bay. The deposit second in size is in the north part of Oxford county. The

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other deposits are in small patches, mostly in the south-western part of the State.

In Westbrook, rather more than a mile west from Portland is a remarkable hill of gneiss which might easily be mistaken for granite. This is near the south-west end of the deposit. Much of the gneiss in Westbrook is deficient in feldspar, and might almost be called mica schist. Proceeding north-westerly in Falmouth and Cumberland its true character appears more distinctly. It is very easy to mistake much of this gneiss for granite. Gneiss is the rock certainly of the following localities in Cumberland and Sagadahock counties, and may embrace more; the south-east parts of Falmouth and Cumberland, and the whole of Yarmouth, Freeport, Brunswick, Topsham, Bowdoinham, Richmond, Woolwich, West Bath, Bath, Phipsburg, Arowsic, Georgetown, Westport, and the south part of Gardiner. The greater part of Lincoln county is underlaid by gneiss. In Knox county, Friendship, Cushing, Warren and Hope, are the towns occupied by gneiss. Lincolnville and Northport are largely occupied by the same rock. It has been traced over to Bluehill across Penobscot bay.

The details of the character and position of the rocks in the different parts of this deposit are not interesting. There is great uniformity in them. The prevailing character of the rocks in the western part of this area is an interstratification of the granitic variety with rather an obscure gneiss. Occasionally the occurrence of beautiful minerals affords a pleasing variety to the eye, as the large crystals of tourmaline in Falmouth, the beryls in Bowdoinham, the garnets and black tourmaline of Brunswick, and the yellow garnets, idocrase and laumonite of Phipsburg. The gneiss in Brunswick is traversed by enormous veins of granite containing large crystals of feldspar which is suitable for the manufacture of porcelain wares. The foliated character of the granitic gneiss may be seen distinctly in West Bath where there are immense beds of this variety. The surface in Bath and adjacent towns along the coast is undulating, but the ridges have a uniform northerly and southerly direction, corresponding in Bath to the course of the strata. The whole of Phipsburg is underlaid by gneiss which is numerously intersected by granitic veins. The gneiss of Lincoln county is not especially interesting. Along the coast the following points and islands are composed of gneiss: Franklin Island, Pemaquid Point, Boothbay, Cape Newagen, Squam Island.