Pyrenees they are being worked quite extensively at the present time.

The mining of manganese ore in this country has so far presented very few legal difficulties, for the simple reason that all the deposits of this mineral have been usually in the eastern portion of the United States, where, as has been stated, the commonlaw maxim of cujus est solum ejus est usque ad cælum prevails. Upon lands belonging to the government there are, however, in the western United States, deposits of very impure manganese ore, which mark the outcroppings of some fissure vein (e. g. near Butte and elsewhere in Montana) or more irregular pockety deposits (e. g. in the Leadville district), as above stated. Should these classes of deposits ever possess value, the law applicable to lode claims would usually prevail, unless, as in the case of some iron or of the more valuable ores, the deposit should be of such a pockety or bunchy, that is to say irregular, discontinuous type, as to make this improper. This will be made clear hereafter in

discussing vein and kindred deposits.

Attention is simply called to the fact that deposits of manganese ore, which are valuable for the manganese which they contain, like some beds of iron ore, are in the great majority of cases found forming distinctly stratified beds or parts of a distinctly stratified stratum, or in the clay derived from the decay of such a stratum; and hence when so found upon government lands it would appear that the law as to the location of a lode claim should not be applicable to them, for the same reason that it should not be applicable to stratified beds or pockety deposits of iron ore, as distinct from iron ore found as the capping of a fissure vein or true lode. When so found, therefore, manganese deposits should, generally speaking, be located as placer claims.

Aluminum. The ores from which this metal is extracted are rapidly assuming commercial importauce. At present there are but two ores of aluminum broadly considered. One is known as cryolite, a large deposit of which is found in Greenland, but which is not common elsewhere. This mineral is composed of sodium, aluminum, and fluorine. As it is not found in large

1 The ore in the croppings of fissure veins is, however, so impure and superficial that it is not likely ever to possess

much value as manganese ore, though it is often valuable for the silver and other metals with which it is associated.

quantities in this country, it does not immediately concern us. It is sufficient to say that if ever found it would probably be found as a veinstone, and, like other veinstones, has been deposited in some crevice from solutions in water.

The other ore of aluminum is known as bauxite, named from the town of Baux in France, where it was first mined in quantity. It is to-day practically the only ore from which aluminum is obtained. It is sometimes referred to as a very pure, though usually indurated, kind of clay in the form of concretions, which, owing to the small amount of silica and of other so-called impurities which it contains, is available for the purposes of making the metal aluminum. Such a clay as is suitable for making good bricks, for instance, is not, on account of the large amount of silica it contains, at all suitable, in the present state of the art, for making aluminum, although it may contain a considerable percentage of the metal.

Bauxite is usually found in segregated masses or nodules (concretions) in aluminous clay, which is sometimes quite pure, but often is more or less impure, representing the decomposition of the superficial portions of some stratum of rock, usually limestone or dolomite (magnesian limestone). It is sometimes, however, found in a more compact form. The minerals which compose it were probably contained in a more disseminated form in the undecomposed or hard rock. When it has had such an origin, it much resembles some of the manganese deposits in the United States in its mode of occurrence and in the superficial, segregated, and nodular character of its deposits. While this theory of origin satisfactorily accounts for many of the phenomena observed in some of the European deposits, it does not apply to all of them, nor does it explain certain of the phenomena connected with the Georgia and Alabama deposits. The origin of these, as well as of the French deposits, is ascribed to the action of mineral springs or geysers. The deposits in the above mentioned States are found in connection with Silurian rocks, usually dolomite, but were very probably formed in Tertiary times through the agency of thermal springs. These waters are supposed to have come up through fault fissures and to have derived the alumina, which they held in solution and brought to the surface, from the underlying calcareous clay shales. This alumina is supposed to have been redeposited in a gelatinous form on or near the surface, during which or after

which deposition the concretions of bauxite were formed. In this way the basin-like character of the deposits is explained. The French deposits, on the contrary, occur in more or less distinctly stratified beds, along with other lacustrine formations and in connection with Cretaceous limestone. They usually contain more iron than the ores of the United States. The chief use to which bauxite is put, however, is not in the manufacture of metallic aluminum, but of alum, q. v.2

Quarries of Building Stone, etc. Quarries of every description that is, of sandstone, limestone, marble, slate, and all other rocks. useful for building or ornamental purposes are regarded, from a legal point of view, in the same light as sedimentary stratified deposits, although technically speaking it is certain that many of them are not of sedimentary origin or stratified. These, for example, are quarries of granite or some eruptive dike, such as trap, or a quarry of a rock formed from the superficial deposition of presumably hot water solutions such as "Mexican Onyx " or the rock"Travertine," of which the city of Paris is largely built, and which has had a different origin from common limestone. The eruptive rocks, however, with the exception of granite, basalt, trap, etc., are not quarried to any great extent, and therefore in a general way it is true that most quarries are of those rocks which form one of a series of sedimentary strata; such, for instance, are the red sandstone (brownstone), slate, and marble (crystalline limestone) quarries of New England. While the outcroppings of a number of fissure veins may be quarried in the western United States, it must not be forgotten that these are simply the outcroppings of lodes, and that they must not be regarded in the same legal sense as a quarry of some common building stone. Legally the common law maxim of cujus est solum ejus est usque ad cœlum, which signifies in effect that the owner's right is complete within the downward vertical extension of his boundary lines, and that

he has no right to mine anything outside of these limits, applies to all quarries when the material quarried is not a part of a lode deposit. For this reason, under the United States law they cannot, when upon lands belonging to the government, be taken up otherwise than as a placer claim, which will be treated at length further on, and to which the above maxim applies in contradistinction to a lode claim. As will be seen hereafter, these two are very different, especially in respect to the rights of the owner with regard to following the ore deposit outside of his boundary lines.

Placer Deposits in General. These deposits are always alluvial or detrital. By these terms is meant that the material forming the deposit is composed of boulders or gravel admixed with sand, and sometimes mud or clay, all of which have certainly been derived from the wearing away of solid rock, or rock in place, further up the ancient or present stream, in the valley of which these alluvial or detrital deposits are found. If one reflects upon what has been said under the head of erosion, it is at once seen that when the rocks in any drainage area contain veins, large or small, or other deposits of metals, these metals or their ores, or the solutions of these, will be carried down with the other material forming the country rock, in the carving or sculpturing out of the valley. If these metals or their ores are quite insoluble in ordinary meteoric waters, it also follows that they will be deposited and will remain with the pebbles or other material forming the alluvial deposit.1 On the other hand, however, if they are soluble in such surface waters, they will be taken into solution and carried off, probably finally reaching the sea, if they should not be redeposited, as will be explained later. Now, generally speaking, there are only a few metals that are with great difficulty soluble in such waters. These are principally gold, platinum, and tin. There are two or three others equally insoluble, such as iridium, palladium, etc., but they are unimportant. All other metals - copper, silver, etc. when exposed for a long time to the chemical action of the atmosphere and surface waters, are slowly taken into solution and carried off, and are not found, at least to any great extent, in such detrital or gravel deposits.

These so-called placer deposits have supplied by far the greater amount of gold that has been produced in the world. They also 1 See further description of formation of gold placers on pages xciv, xcv.

supply practically the entire amount of platinum and most of the tin of the world. In the case of the latter metal, however, instead of being in a pure or native state, it is found in the form of tin ore or the so-called "tin stone" (oxide of tin), which, like the pebbles of phosphate rock already described, is soluble with great difficulty, and is therefore left behind with the other insoluble matter, such as the ordinary quartz and other pebbles or sand with which it is associated.

Diagram showing Origin of Auriferous Gravel.

These stratified beds of gravel or so-called placer deposits are of such vast commercial importance that they deserve to be treated of in some detail, and classified by the name of the metal for which they are worked. The description above given is sufficient to give a general idea of what they are.

Gold Placers. As above stated, a very large portion of the gold of the world is derived from this source. In our western country gold to the value of hundreds of millions of dollars has been taken from various placer deposits which have been worked with varying success since the discovery of gold in this form in California. These placer gravels have been in some cases consolidated into hard rock, forming a bed of grit, or conglomerate, as it is called. But usually these gravel beds are as yet in an unconsolidated state, and are therefore easily washed down by the action of powerful jets of water. The accompanying illustration gives an idea of how such a gravel bank is attacked. They are often worked, however, in other and very much more primitive ways. In many cases the gravel is overlaid by a flow of lava, which is of course now in the condition of hard rock, and has in itself prevented the washing away of many important gold bearing gravel beds. An illustration of this is also given to show two things: first, the great amount of material removed by erosion; and, second, that the present mountain top was once the bottom of a river, the valley of which was afterward followed by an outpouring of lava. No doubt these placers give rise to other