twenty pounds was found, while I was at the Cerillos, to which the wyth was still attached, with its oak handle-the same scrub oak which is found growing abundantly on the hillsides now, and quite well preserved, after at least two centuries of entombment in this perfectly dry rock.

The stone used for these hammers is the same hard hornblende Andesite or Propylite, which forms the Cerro d'Oro and other Cerrillos hills, very hard and tough. With these rude tools and without iron and steel, using fire in place of explosives, these patient old workers managed to break down and remove the incredible masses of these tuffaceous rocks which form the mounds already described.

That considerable quantities of the turquoise were obtained can hardly be questioned. We know that the ancient Mexicans attached great value to this ornamental stone as the Indians do to this day. The familiar tale of the gift of large and costly turquoise by Montezuma to Cortez for the Spanish crown, as narrated by Clavigero in his history of Mexico, shows the high value attached to this gem. It is not known that any other locality in America has furnished turquoise in any quantity-the only other place outside of Los Cerillos, where it is found at all, being that near Columbus District in Nevada, discovered by Mr. J. E. Clayton, and this has not been worked as yet.

The origin of the turquoise of Los Cerillos in view of late. observations is not doubtful. Chemically it is a hydrous alumi num phosphate. Its blue color is due to a variable quantity of copper oxide derived from associated rocks. I find the Cerillos turquoise contains 3.81 per cent. of this metal. Neglecting this constituent the formula for turquoise requires: Phosphoric acid, 32.6; alumina, 47.0; water, 20.5. Total, 100.1.

Evidently the decomposition of the felspar of the trachyte has furnished the alumina, while the apatite, or phosphate of lime, which the microscope detects in the thin sections of the Cerillos rocks, has furnished the phosphoric acid. A little copper is diffused as a constituent also of the veins of this region, and hence the color which that metal imparts.

The inspection of thin sections of the turquoise by the microscope, with a high power, shows the seemingly homogeneous mass, of this compact and non-crystalline mineral, to consist of very minute scales, nearly colorless, having an aggregate polarization, and showing a few particles of iron oxide.

The rocks in which the turquoise occurs are seen, by the aid of the microscope and polarized light, in thin sections, to be plainly only the ruins, as it were, of crystalline trachytes showing remnants of felspar crystals, decomposed in part into a white kaolin-like substance, with mica, slag and glassy grains, and quartz with large fluidal enclosures, looking like a secondary product. There is considerable diversity in their looks, but they may all be classed as trachyte-tuffs and are doubtless merely the result of decomposition, as already indicated, of the crystalline rocks of the district along the line of volcanic fissures. In fact there are in the northeast direction other places, one of them at Bonanza City, a distance of probably two to three miles, where the same evidence of decomposition is found, and in the rocks at this place I find also the turquoise in forms not to be distinguished from that of the old mine. Mr. Hyde has shown me lately in New York a large number of the Cerillos turquoise polished, one of huge size; and among them a few of good color and worthy of consideration as gems, some of them an inch in length and quite thick, but they are not of faultless beauty.

THE ISLAND OF MONTREAL AN ISLAND, NOT IN THE ST. LAWRENCE, BUT IN THE OTTAWA. BY WILLIAM BOYD, of Cambridge, Mass. THE waters of the Ottawa, at the foot of the Lake of Two Mountains, divide on the Island of Montreal into two branches of nearly equal volume. The lesser branch-making for the south of the island, and also for several miles farther south along the Vaudreuil shore to Cascades Point-subdivides on Isle Perrot, an insulation of seven or eight miles in length (from west to east) and from two to three miles in breadth, lying south, and part of it west, of the head of the Island of Montreal. There are rapids in each of the sub-branches. The southern branch of the Ottawa encounters the St. Lawrence at Cascades Point; and also at the foot of Isle Perrot, where the sub-branches reunite. From Cascades Point and the foot of Isle Perrot the Ottawa water flows in the same bed as that of the St. Lawrence, of course on the

northern side of the St. Lawrence water,-filling from a quarter to a third of that bed; which fact is evident from the difference in

Map showing how the waters of Ottawa surround the Island of Montreal. Note direction of arrows.

of a brownish, that of the St. Lawrence of a greenish, hue. The two river-streams run side by side unmixed to the Ottawa's lowest mouth, at the foot of the Island of Montreal, where this southern stream or branch of the Ottawa joins the northern branch of the same river. (Thence these river-streams flow onward, side by side, as before, the Ottawa's stream doubled in volume,—to Lake St. Peter, where they commingle in its slack water and the tidal head.) If the River Ottawa should cease to exist and the River St. Lawrence should remain, what is now the Island of Montreal would probably from the high level above St. Anne and below Vaudreuil of the bed of the then extinct Lake of Two Mountains, and from the very considerable fall which would on the disappearance of the Ottawa take place in the St. Lawrence below the Cascades Rapids-be an island no longer; but if the St. Lawrence should cease to exist and the Ottawa should remain, what is now the Island of Montreal would be an island still.

From the above facts the writer concludes that the Island of Montreal is an island, not, as has heretofore been held, in the St. Lawrence, but in the Ottawa.

THE LAW OF LAND-FORMING ON OUR GLOBE. BY RICHARD OWEN, of New Harmony, Ind.

THE object of the present paper will be to state the law by which dry land shows itself above the ocean, and to sustain that statement by so many coincident facts, which can be traced on any good globe, or on large maps of separate continents, as to satisfy the scientist that the law is of universal application to geographical and geological phenomena, with few, if any, exceptions:

General Law: The land on our globe shows itself above the ocean level, in definite multiple proportions, by measurement; the unit is the angular difference between the axis of rotation and the axis of orbital progression.1

For convenience, as that angle has been lessening for centuries, we might call it 24° We then have:

=24°56.0°

The geographical and geological unit
Greatest width and length of continents = 3 X 21° 72° = 350°

Radius for continents
Half radius

36°

360°

10

= 18° 30°
20

The measure for oceanic distances is the complement of 24°C6°. The ratio of land to water, as shown by Prof. Dana, is as 100: 275. The ratio of 24° 66° .: 100: 275. All measurements are to be estimated at the equator.

To render the demonstration of the above general law more intelligible, it may be advantageous to consider it under several separate heads, or subdivisions, following up each of these heads or sections, by its demonstration.

I. First subdivision or section of the law: Many longitudinal elevations and depressions on the earth's surface (the result apparently of cooling and contraction), especially near the greatest median extension of each continent, north and south coincide with some meridian. Consequently, if we conceive the planes of these great circles produced to the earth's axis, the terminal axis. of the spherical wedges thus formed would coincide with the axis of rotation. Further, this shrinkage has caused a north and south continent to appear in each of four equal spherical wedges of our earth, estimating the 90° for each wedge on the equator. Minor north and south extensions can be traced at intervals, often of 43° or 9° apart, all around the globe, alternating usually, at least on the continental outlines, with trends which form with the meridians, angles of about 234°.

Demonstration: After placing the artificial globe in such position that the terrestrial poles are at the wooden horizon, and the eastern extremity of Brazil at the brazen meridian, we find North and South America occupying one quarter, Europe and Africa a second, Asia and Australasia the third, while the fourth embraces North and South Oceanica, which may be regarded, either as a sunken continent, or as an ocean with north and south island groups.

In Europe and Africa combined, we find the greatest median elongation in about long. 21° to 22° E. of Gr. In Asia, the median elongation is about in long. 99° to 100° E. In North America, it is in long. 96° W., in South America in long. 69° to 70° W. In N. Oceanica, the elongation is from Point Barrow, through the Sandwich Islands to Tahiti, therefore in about long. 155° W.; lastly for Australasia, the elongation is about in long. 144° to 145° E.

To prove the minor north and south extensions, on coast lines as well as through continents, we may begin anywhere on the equator, and trace, north and south, great circles at intervals of about 9° apart. We find, likewise, evidences of alternate elevations and depressions: a great elevation in one continent seeming to have resulted in a depression on the opposite side of the globe. To give a single example, follow the immense heights of the