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four cats, two young dogs, two young rabbits, five rabbit embryos, and of a number of butterfly chrysalides, and the amount of soda and of potash in different articles of food was found. From the numbers thus obtained, and given in tabular form, interesting conclusions were drawn, in regard to the relation existing between the food and the composi tion of the body, as regards the amount of the alkalies and chlorine present. In vegetable food the excess of potash over soda, compared by equivalents, is much greater than in human milk, or those in that of herbivorous animals; so that, if the proportions of potash and soda in milk are to be considered as the most favorable to nutrition, the addition of salt to all the more important vegetable articles of food is indicated. The amount of soda in the organism varies within as wide limits in the animal kingdom as in the vege table, and the amount of soda, potash, and chlorine in milk is not constant, but varies with the food and other conditions. The young of the carnivorous animals receive in their milk potash and soda, and generally all the fixed ingredients, in almost the same proportions required for their growth; and while in the bodies of the young of herbivorous animals the relative amounts of soda and potash are found to differ from those of the carnivorous animals, the relative amounts of these substances secreted in the milk by which they are nourished conform to this difference. Prolonged feeding, however, upon substances rich in potash and poor in soda will increase the relative amount of the former in the milk.-19 C, Jan. 23, 1875, 35.

E. MINERALOGY AND GEOLOGY.

66
POT-HOLES, OR GIANT KETTLES.'

It is not always that geological investigations have as their object phenomena which are of general interest, and with which all are more or less familiar. This is certainly the case, however, with the study of the "giant kettles" in the neighborhood of Christiania, Norway, which has been lately carried on by Professor Kjerulf and some of his students. There is hardly a running stream in our country of any considerable size which does not give proof of the power of water and stones in motion in what are popularly called "potholes." An eddy in the stream where the current is strong sets a few pebbles in revolution. These commence a depression, into which larger stones fall, and the grinding is continued until a cavity has been produced perhaps several feet in depth, and almost perfectly round. These are often to be observed, not only in stream beds, but also in rocks on the sea-shore, where the rush of the tide must, supply the motive force.

The famous "giant kettles" of Norway are simply "potholes" on a larger scale, and produced in former times under somewhat different conditions than we have at present. The superstition of the people represents them as having been made by giants. In some places, where the form is oblong and irregular, fancy has seen in them the footprints of these monsters, while in one place, where the road goes directly through a very large kettle, the saying is that there St. Olaf turned his horse around. On the west coast of Norway another name is used, and they are spoken of as giants' chairs,

The description of one of these kettles examined by Professor Kjerulf will give some idea as to their size and general character. At the surface it had a diameter of about eight feet, being slightly elliptical in form. It widened considerably on the descent, and then contracted again at the bottom. It is interesting to note that the walls were distinctly. worked out in a spiral, which could be traced from top to

bottom. In the case of some other kettles examined, the spiral was so perfect that the cavity could be compared to the impression of a gigantic snail.

The total depth of the kettle in question from the highest point of the margin was forty-four feet, the axis inclining somewhat toward the west. It was filled, as is always the case, with gravel and broken rock, though toward the bottom numerous so-called grinding-stones were found, some of them 300 pounds in weight, and all smooth and elliptical in shape. It was through their revolution that the excavation had been made. It required three men, working for fifty days, to clear this giant kettle of its contents, and the whole amount taken out was estimated at 2350 cubic feet, some of the stones being so large that they had to be mined before they could be hoisted out.

The kettles, in general, present much the same features as the one which has been just described, though there is a great variation in ratio of width to depth, many of them being shallow, larger at the top than at the bottom, and very properly are called kettles, while others, as the one alluded to, are deep, and could better be called wells. It is to be observed that they are by no means necessarily found in present river channels. They are most common in the neighborhood of the great fiords, though they have been observed too at a height of 1200 feet above the sea. In regard to their origin, the best authorities refer it to the time when the land was covered by enormous glaciers, such as now exist in the upper part of Greenland. The melting of the ice on the surface of glaciers gives rise to considerable rivers, and as these find some crevice in the ice, they descend with violence, and it is conceivable that such a stream striking the bed rock below might be the means, with the masses of rock they would put in motion, of producing the enormous cavities which are now observed. This theory, as carried out by its supporters, meets with some difficulties, but seems to be the best which has been proposed.

PROBABLE AGE OF THE CRYSTALLINE ROCKS OF THE SOUTHERN APPALACHIANS.

Professor Bradley, of Knoxville, Tennessee, has recently published the results of his geological labors among the

Southern Appalachians, which throw much light upon the probable age of the crystalline rocks of that region. It has long been the tendency of geologists to regard the metamorphic crystalline rocks of the Atlantic coast as certainly pre-Silurian. This has, however, been called in question by the observations of Professor Dana, which go to prove that the limestones and accompanying schists and quartzites of Western New England are all Silurian, and not Huronian nor Laurentian. Professor Bradley now claims the same for the region he has investigated, that is, the western portion of North Carolina, the eastern part of Tennessee, and much of Georgia and Alabama. The evidence upon which the conclusion is based is stratigraphical, and must be studied in detail to be fully understood. The time at which the uplift and metamorphism of this region took place is considered by Professor Bradley to have been post-carboniferous, and it is probably referable to the close of the paleozoic.

DISCOVERY OF A BED OF NICKEL IN NORWAY.

It is announced that a very rich bed of nickel has been re'cently discovered in the forest of Glörud, in Norway. The ore proves to contain 3.59 per cent. of pure metal, an exceptionally large proportion.-13 A, September 4, 1874, 263.

MAGNETIC SAND IN LABRADOR.

It is stated that, within a few years past, large quantities of magnetic iron ore, in sand, have been discovered on the north coast of Labrador, and that Mr. Lamothe, of Montreal, has more recently been engaged in bringing this to public notice. A company was formed, and forges were built at Moisie, which are now in operation, since when other localities have been determined along the north shore, especially at Matashquan, Kegashka, St. John River, and St. Marguerite. Several attempts have been made to purify this sand in a rapid and economical manner, and to make steel from the ore by a direct process, and these problems have now been solved by Professor Larne and Mr. Kizer, of Montreal. An establishment has also been erected at Block Point, between St. John River and Mingan, for the preparation of the sand and its exportation to Swansea. It contains, in the rough state, 30 per cent. of the magnetic iron, and when prepared

99 per cent. It is expected that thirty tons per day will be furnished at this place. Works for the manufacture of steel from this sand have been established at Quebec, and at Matashquan others are being put up. The ore is said to excel that of New Zealand in richness, and it is probable that before long it will occupy a permanent place in the iron industry.

INTERESTING PHENOMENA OBSERVED IN STONE QUARRIES. Professor W. H. Niles, of the Boston Institute of Technology, communicates the results of further observations of the peculiar phenomena observed at the stone quarries at Monson, Massachusetts. Similar phenomena have been recorded once before by Professor Johnston, of Middletown, Connecticut, in relation to the sandstone quarries at Portland, in that state. Both these gentlemen concur in the same conclusion, namely, that the strata of sandstone at Portland and the strata of gneiss at Monson are not at the present time perfectly at ease in their ancient beds, but that, in some way, they have received a disposition to change their position slightly; that, in fact, they exist there in a state of compression, the force with which they tend to expand being so great that it has been known to break apart beds of the thickness of three, four, and five feet, for a distance of 100 feet or more; while in another case one end of a long prismoid of gneiss, being solidly attached to the undisturbed rock, the other end, by its expansion, pushed upward about 10,000 tons of rock. The expansions at Monson take place only in a northerly and southerly direction. The cracks and rents are generally formed slowly, but sometimes suddenly, attended by a loud report similar to that of a slight shock of earthquake, and sometimes by the throwing of stones of considerable size to the distance of several feet.-Proc. Am. Assoc., I., 1873, 156.

CHANGES OF LEVEL ON THE COAST OF MAINE.

For many years there have been reports of changes in the depth of water on the rocks and shoals on the coast of Maine. From a report on this subject to the Superintendent of the Coast Survey, by Professor Shaler, the following facts have been gathered:

The natural indications of changes of level are the remains

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