be distinguished on account of its ammonia above that of the ocean in an east wind.

Continued observations on the state of the atmosphere, made since the reading of this paper before the American Association, show that the quantity of ammonia in the atmosphere is subject to constant variation. In the summer, when vegetable and animal decay is most rapid, the quantity is at a maximum, and afterwards decreases regularly until the winter season, when it is at a minimum. The following table shows the amount of ammonia found in the atmosphere at thirteen different analyses.

SINGULAR COMBINATION OF NITROGEN.

WOHLER, of Germany, has ascertained that the crystals found in the slag of some furnaces, and supposed to be pure titanium, contain both carbon and nitrogen in proportions corresponding with the formula Ti Cy + 3 Ti3 N. This fact gives us entirely new ideas of the nature of nitrogen, a body supposed to be distinguished above all others for its tendency to take on the gaseous form when its compounds are subject to heat.-Letter of Prof. Liebig to Prof. Horsford.

19*

GEOLOGY.

GEOLOGICAL SURVEYS OF THE UNITED STATES.

AT the recent meeting of the American Association, resolutions were offered, strongly urging the completion of geological surveys of the several States of the Union which still remain unfinished. There are several cases of this kind, and the interests of the State, the country, and of knowledge, strongly demand that the work be carried forward. Large portions of our territory, rich, it may be, in wealth of minerals, building material, fertile soil, and various productions valuable in the arts, remain unexplored, and, where explorations have been made, there have been delays in the publication of reports, which are not creditable to the legislatures that have this matter in control, nor just to those who have been laboring in the surveys.-Silliman's

Journal.

GEOLOGY OF THE GOLD REGIONS OF CALIFORNIA.

THE following account of the geology of the gold regions of California is compiled from various sources. The region of the Sacramento is remarkable for the great extent of its alluvial plains or flats. Two hundred miles from its mouth they are twenty miles wide, but near Sutter's Fort the width is between fifty and sixty miles. The country about Sutter's Fort during the winter is mostly covered with water, and the same is true of the bottom-lands of the rivers of the gold region. All the gold thus far discovered occurs uniformly in one geological formation. This is the stratum of drift, or diluvium, composed of a heterogeneous mixture of clay, sand, gravel, and pebbles, and varying in thickness from a few inches to several feet. There are many boulders lying directly beneath the soil, and resting on the rocks below, which, in most of the diggings, consist of gneiss or clay-slate, running about north-northwest and south-southwest, and dipping nearly perpendic ularly. The stratum of diluvium is, however, neither horizontal nor of uniform slope, but conformed to the varying inclination of the

earth's surface, covering the declivities, and even the summits of the hills, as well as the bottoms of the ravines and valleys. The sandbars of many of the mountain torrents are extremely rich in metal. Quartz is believed to be the only substance with which the gold is intimately connected. The gold of different localities varies very much in size. That from the banks and sandbars of the rivers is generally in the form of small, flattened scales, and commonly it is found to be finer the lower you descend the stream. That taken from the bottom of dry ravines is mostly of a larger size, and occurs both in small particles and also in small lumps and irregular water-worn masses, from the size of wheat-kernels to pieces of several ounces, or even pounds, in weight. The black, ferruginous sand, which everywhere accompanies the gold, varies in fineness with the size of the accompanying gold.

The slate beds mentioned above often include dikes or beds of quartz rock, in which some have asserted that gold has been found in place, but this still wants confirmation. In some of the richest ex-. plorations yet made, however, the slate directly underlies the stratum of diluvium mentioned as containing the gold, and this slate has many crevices or "pockets," into which the gold has been washed in considerable quantities, and this fact also has given rise to the belief that gold has been found in place.

There can be little doubt that the gold was deposited in its present position by the same agency and at the same time as the stratum in which it occurs. It is a peculiar fact, that some specimens have been found which appear to have been moulded on regular quartz crystals.

To the east of the gold regions are the mountains of Sierra Nevada, consisting of primitive and metamorphic rocks. In the vicinity of these mountains, the gold and its associated quartz disappear; the rocks underlying the drift appear to consist entirely of gneiss, which is afterwards succeeded by granite.

North of the Bay of San Francisco, talcose slates of various colors have been noticed, and also hills of red and yellow jasper, in layers varying from half an inch to four inches in thickness. At the Straits of Caquines, bluffs of red sandstone, alternating with clayey layers, occur. This sandstone, which is believed to belong to the eocene period, is soft and easily worked. On a small island near these Straits, gypsum has been found in considerable quantities.

In a letter, dated at San Francisco, October 29th, and published in Silliman's Journal for January, 1850, received since the above was written, Rev. C. S. Lyman states that "gold has at last been discovered in place,-in veins penetrating quartz beds,—on the Mokelemnes and in the vicinity of the Mariposa and one or two other places. I have this from gentlemen who have seen the veins, and who are reliable witnesses. These veins are of course not worked yet, as it is more profitable to dig the wash-gold.”

The Pacific News for November 30th, states that "quartz containing gold has been found in inexhaustible quarries through the whole mountainous region which forms the western slope of the Sierra Ne

vada. Hon. T. Butler King has spent much time in examining this region, and is about making a report upon it to the government at Washington; it will be accompanied by numerous specimens. We have ourselves examined specimens from these quartz mountainquarries, which are in the possession of Mr. Wright, one of the members of Congress elect from California, who will take them on to Washington. They consist, for the most part, of small pieces of quartz rock, generally of a brownish tinge, and, in some instances, presenting the appearance of a slight incipient decay, or decomposition of the rock formation. In all these specimens the gold points, or particles, are very slightly, if at all visible to the naked eye. The microscope, however, reveals the gold more clearly. Besides these pieces, which Mr. Wright has himself selected with great care, as the fairest average samples of the general appearance of enormous and very numerous veins, or quarries, of quartz, there is also one larger fragment of the same rock, weighing, we should suppose, some ten or twelve pounds, from all parts of which the gold protrudes plainly in a state almost pure. This single fraction of quartz, which Mr. Wright by no means regards as an average sample of the quarries, but which he pronounces to be the richest rock-specimen he has seen, is found by the most careful specific-gravity test, as applied to it by Mr. Wright, to contain pure gold to the amount of about six hundred

dollars.

"Mr. Wright has spent much time among the mountains collecting his specimens, and has been assisted by a gentleman conversant with mining operations. The astonishing result brought out by these investigations, is, that, in a particular and very extensive vein, four pounds of this rock yielded, upon the average, $11 worth of pure gold, valued at $16 to the ounce; that is to say, the yield of gold from these average samples of the rock in this particular vein is nearly $3 for each pound of quartz. Mr. Wright exhibited to us two small masses of gold, each about the size and shape of a large musket-ball, and both presenting the granulated appearance of gold extracted and collected by the aid of quicksilver. One of these contains about $12 of pure gold, and is the largest yield which has been obtained from 4lbs. of the rock in question. The other contains about $10, and is the smallest yield which has been obtained from any of the experiments upon the rock of this vein. We understand that the tests applied have been sometimes the operation of quicksilver, and sometimes the test of the comparative specific gravity of the pure quartz and the gold-bearing quartz." The Secretary of the Interior remarks, in his Annual Report:"The gold is found sometimes in masses, the largest of which brought to the mint weighed 89oz. They are generally equal to the standard of our coin in purity, and their appearance that of a metal forced into the fissures and cavities of the rocks in a state of fusion. Some masses, however, are flattened apparently by pressure, and scratched as if by attrition in a rough surface. One small mass which was exhibited had about five parts in weight of gold to one of quartz intimately blended, and both together bouldered so as to form a handsome rounded pebble, with a surface of about equal quartz and gold.

A very large proportion of the gold, however, is obtained in small scales, by washing the earth which is dug up on the beds of the streams or near their margin. A mass of the crude earth, as taken at random from a placer, was tested by the Director of the United States Mint at Philadelphia, and found to contain 2644 grs. of gold, being in value a fraction over $10 to 100lbs. It cannot, however, be reasonably supposed that the average alluvial earth in the placers is so highly auriferous.

COMPARATIVE STRUCTURAL FEATURES OF THE APPALACHIAN

MOUNTAINS AND THE ALPS.

AT the meeting of the American Association, Professor H. D. Rogers presented an important communication on the "Structural Features of the Appalachian Mountains, compared with those of the Alps and other disturbed Districts of Europe." The characteristic features of the Appalachians are, that on their southeast slopes the strata are invariably doubled into oblique flexures or folds. Farther towards the northwest, or central belts of the chain, these flexures are less perceptible, but the inverted or northwestern side of the anticlinal curves dip much more steeply than the southeastern. Advancing still farther across the chain, these great flexures or arches of the rocks progressively expand, the curvature of the northwestern slopes still, however, dipping very steeply, while in the broad plateaus of the Alleghany and Cumberland Mountains the arches or waves subside and dilate into symmetrical undulations of equal and gentle curvature. Along all the southeastern border of the chain, the prevailing dip is therefore toward the belt of active igneous movement, where alone the strata are perforated by intrusive volcanic rocks. These arches or waves are of great length, and, whether straight or curved, exhibit a singular degree of parallelism and uniformity in their style of flexure. In the southeastern and middle zones of the chain, many of these great arches terminate in enormous longitudinal faults or fractures, which are nothing else than inverted flexures broken at some point in the inverted part of the anticlinal, producing the apparent anomaly of an overlapping of newer strata by others of far older date. Some of these fractures thus ingulf a thickness of nearly two miles. The cleavage planes of the rocks are nearly parallel with the average dip of the planes which symmetrically cut or bisect the anticlinal and synclinal curves; and this law of position of the cleavage planes is found to prevail equally in the plicated districts of the Rhine and the Alps. Precisely analogous features to those which have been observed in the Appalachians have been proved to belong to the paleozoic region of the Ardennes, and the coal-fields of Belgium. In the more disturbed tracts the strata are closely and sharply folded into almost absolute parallelism, while farther north, in the carboniferous basins of the Meuse, these flexures dilate precisely as in the sections of the Alleghanies. The cleavage planes of the more contorted belt are, as in the Appalachian region, planes which divide the curves, parallel to the average dip of the axes. In the Jura, the same beautiful law of a