specimen of a Trilobite (Paradoxides Tessini or Harlani) which was obtained by him from the slate quarry at Braintree on the 9th August last. He also exhibited a cast of a specimen of the same species, which from the character of the rock was undoubtedly obtained from the same ledge, and which was purchased by Mr. Francis Alger at the breaking up of the old Columbian Mu seum of Boston, some twenty-five years ago, and was originally presented to that Museum by some one residing in this vicinity. Mr. Alger's specimen is in a sharp angular prismatic mass of rock, having all the appearances of having been broken from the rocks in place, and certainly was not a boulder.

From the existence of this specimen, and also from the frequent discovery of fragments of trilobites in the erratic rocks on George's island, Geologists were prepared for the discovery of them in some of the ledges of this neighborhood, but no one ever thought of looking among the pinched-up and metamorphic slates between the Quincy and Braintree sienite hills for any fossils, until they were actually disclosed by the quarrying operations of the Messrs. Haywood at Braintree, and one of our members, Peter Wainwright, Esq., recognized them as trilobites and as subjects of great scientific interest, and called the attention of professed Geologists to the locality.

About five years ago, Mr. Eliphas Haywood first observed. these fossils on opening his stone quarry for the purpose of ob taining underpinning and ballast stones. Without knowing their nature, he still looked upon them as interesting curiosities, and laid aside the specimens which have lately been brought before the Society.

He showed them to Mr. Wainwright, who at once recognized them as trilobites and brought them to Boston for the inspection of Geologists, and presented two specimens to our associate, Prof. Wm. B. Rogers, to whom the Society is indebted for the first notice of these remarkable fossils, so important in the determination of our geognostic horizon. A few days after Prof. Roger's visit to the quarry, Dr. Jackson, by invitation of Mr. Wainwright, visited it and made a minute examination of all the geological phenomena which it presents, and obtained specimens of the trilobites through the kindness of Mr. Haywood, and by search at the quarry in company with Mr. Wainwright. Two specimens were obtained, one entire, which is 8 inches long

and 4 inches wide.

The other, of which only the head and half the body was obtained, is 6 inches wide, and its hood is 7 inches across by the base of the head; hence the length of this specimen must have been 12 inches at least, which is about the size of the largest specimens of the Paradoxides Tessini discovered in Sweden. The smaller individual has 21 articulations, but none in the tail beyond the lateral appendages, and in this respect differs

from the P. Tessini, its nearest analogue, which has, according to Brongniart, four faintly marked depressions or folds crossing the tail transversely. They may have been obliterated in our specimen by the changes the rock has undergone. These trilobites of Braintree occur in a blue gray argillaceous slate, containing silicate of lime, but no carbonate, and some disseminated iron pyrites. The stratification of the rock, as indicated by its grain and cleavages, dips to the north 50°, and runs east and west. It is but slightly altered by heat in those portions where the trilobites are found, but near the sienite rocks it is filled with nodules of epidote, and closely resembles the altered slates of Nahant. There is a small vein of quartz, bearing iron pyrites in it, which cuts through the slate strata at right angles. There are also slickensides surfaces on some of the cleavages or joints in the quarry, indicating, as it is supposed, the polishing effects of rapid earthquake movements at the period of disturbance of the strata at the time of their disruption by intruded sienite.

These are all the marks discoverable of metamorphic action of igneous rocks on these sedimentary strata, though the slate rocks are hemmed in by the sienite rocks on both sides, and the belt of slate is quite narrow.

On a hill near the quarry he could see the tall steeple of the Baptist church in Somerset street, and on taking its bearings with the compass, it was found to be N. 10° W., and Nahant would be a little to the East of North. The Braintree rocks would then dip under those of Nahant, unless the same formation extended across the bay, and the Nahant series would form its upper strata.

The existence of these Paradoxides in the argillaceous slates of Braintree proves them to belong to the lowest of the fossiliferous silurian rocks, and that they are the geological equivalents of the argillaceous slates of Sweden, which are in a similar manner disrupted by the intrusion of sienite. It is certainly interesting to find the base of the Silurian system resting within the limits of old Massachusetts.

ART. IV.-REPORTS AND EXPERIMENTS ON THE STRENGTH AND OTHER PROPERTIES OF METALS FOR CANNON, WITH A DESCRIPTION OF THE MACHINES FOR TESTING METALS, AND OF THE CLASSIFICATION OF CANNON IN SERVICE.-BY OFFICERS OF THE ORDNANCE DEPARTMENT U. S. ARMY. By Authority of the Secretary of War. HENRY CAREY BAIRD: Philadelphia, 1856.

THE question "What is the best material for the military arm of a nation?" is one of national and vital importance: because the

demonstration of the war aspect of the question gives us corollaries for the determination of points essential in the arts of peace. Our government, in experimental science, is certainly ahead of European ones; and the solution of this national question engaged official attention many years since. The work (the title of which precedes this article) is the result and deductions of long and practical series of experiments alike creditable to our government and the officers and gentlemen co-operating in the investigation. This work, also published by Trübner & Co., London, is evincive of the fact that it is appreciated abroad; and we know it has received the most favorable critical notices from the scientific and practical periodicals of Europe. It is quoted in military and naval journals as standard authority, and has aroused a similar spirit of investigation in several European governments; and as the ball rolls on we may hope for some splendid deductions of applied science and an augmentation of mineral economic wealth.

We leave to the military journals to discuss and illustrate, if they can, the position that the amelioration of the savageness and miseries of war is increased by the improvement and increased destructiveness of weapons of war-and that by the assured certainty of destruction of life-the less will be the ultimate loss of it; or, in other words, the moral certainty of death will increase the moral aversion to exposure to it. While we thus avoid a discussion of this question, we do not hesitate to say, that such experiments and trials have a moral aspect of the highest character. The elimination of the elementary composition of metals for war purposes cannot fail in presenting facts and corollaries of essential value in the arts and commerce of life. In its utilizing and peaceful character, we propose to add our commendation of the great practical value of this work.

The investigations were commenced nearly simultaneously with the organization of the Ordnance Corps, and the earlier results were published in the "Ordnance Manual" of 1840. The volume before us gives us a series of most interesting reports commencing as late back as March, 1844. We are glad of the opportunity in this place to add our testimony to the great value of our West Point Military Academy in its contributions to the exact and applied sciences of our country. For whatever exactness and profound and critical analysis this volume affords us in these experiments, we may trace to the influence of the system of instruction maintained in that noble and national Institution.

The earlier investigations were mainly directed to the manufacture and patterns of guns, and the methods pursued at the dif ferent foundries in Europe and the United States. From these investigations it was ascertained that of a series of guns made of the same material, pattern, and identity of process, some would bear the maximum test without injury, while others supposed to VOL. VII.-28

be exactly, and in all respects like them, would not bear proof charges, or failed after a few rounds. The failure then was not due to the material or its treatment during the process of manufacture, but to a cause remote, and not ascertained, but supposed, from the facts elicited, to be in the ore from which the iron was made.

We should here premise that one result of the experiments was that cast iron was the safest and best resource for heavy seacoast siege and garrison cannon; and for the lighter field-pieces it was resolved to adopt bronze as a material least likely to burst into fragments.

For the purpose of ascertaining the variety of influences arising from the varieties of the crude material or ore, or, in the language of the report, "to determine the causes which so materially affect the quality of gun metal," a laboratory was established at Pekesville, and in it every means was adopted to insure accuracy and completeness in the results. It was devised with a view to the qualitative and quantitative examination of each specimen, and was so arranged that any ingredient existing in gun metal, even in minute proportions, could not escape detection during the process of manipulation.

From these experiments and tabular deductions, it seems that the total carbon proves nothing in favor of its influence upon the quality of the iron, although further examination may, perhaps, modify this conclusion. There is, however, a decided relation of the carbons in their separate states to specific gravity and tensile strength. Allotropic carbon increases, and the combined carbon decreases; and this excess of allotropic carbon must exist as graphite or black lead, which is injurious. The extremes of the amount of carbons as affecting the increase or diminution of the excellence of the quality of the metals, their influence upon its molecular construction, and the possibility of their being replaced by some other ingredient, are matters of great importance, and still under investigation. In the table exhibiting the effects of hot and cold blast, it appears the hot blast has driven off a portion of carbon from combination, so that the cold blast metal contains two and three-fourth times as much combined carbon. The hot blast metal, however, meets with some compensation for this loss of carbon by reducing by its intense heat a larger amount of silica, and assuming silicium. The hot blast contains nearly four times as much slag as the cold blast: and the slag and allotropic carbon being of a brittle character, and not uniting with the iron, coat the crystalline plates of metal, and diminish the surface contact, and consequently tensile strength-which strength is also further diminished by the replacement of carbon by silicium. The ave rage specific gravity of the hot blast iron appears to be 7.065, and the tensile strength 19.640. The average specific gravity of the cold blast was 7.218, and the tensile strength 29.219. The ex

traneous matters found in combination with the iron were allotropic carbon, combined carbon, silicium, calcium, magnesium, sodium, potassium, cobalt, nickel, manganese, aluminium, copper, phosphorus, tin, titanium, antimony, sulphur. On this point of the relative value of hot and cold blast iron, the general deduction thus far appears to be that the hot blast is inferior to cold blast, by reason of the relative excess of slag and allotropic carbon.

The ores of iron contain that metal in the state of oxide, accompanied more or less by earthy matter. These oxides are the magnetic or protoperoxide, and containing, when pure, the highest amount of metal. The peroxide, which when crystalline is called Specular, and Red Hematite when earthy-the Hydrated Peroxide or Brown Hematite-Bog ore and Pipe ore; the carbonate of the Protoxide. which when crystallized is sparry, and when earthy is the coal ore, or clay ironstone.

The best practicable division is based upon the largest amount of associated matter. 1st. Silicious, with silica as the earthy constituent, including most of the magnetic and specular oxides. 2nd. Calcareous, which are usually very silicious, and include the Red Hematite. 3rd. Magnesian, with Talcose gangue of magnesia and silica, and the iron as magnetic oxide. 4th. Argillaceous, containing alumina and silica, and include the earthy brown hematite and clay iron stone. 5th. Manganesian, includ ing the sparry and brown hematites.

In reducing iron ores the oxide is reduced to metal, and its associates are fused into slag or cinder by the use of limestone as a flux. All the ores contain silica; but when it is alone, or associated only with lime or magnesia, as in the first three classes, the fluxion of the earthy matter, and consequent reduction of earthy constituents, is attended with difficulty. Hence, such ores are termed hard; on the other hand, when the silica is associated with alumina or oxide of manganese, as in classes four and five, the slag is more fusible, reduction facilitated, and the ores called soft.

The ores of the second class (calcareous) are often so very calcareous that the use of limestone as a flux is unnecessary and injurious. In such cases where an argillaceous or manganesian ore is not to be obtained, the addition of clay itself renders them more easy of reduction, and the clay may be regarded as a flux.

As a general rule a single ore rarely contains the ingredients in due proportion required to flux it readily, and hence the utility of mingling different kinds of ores. Either of the first three may be advantageously mixed with either of the two latter classes.

The process of reduction is as follows: The ore, flux and fuel being thrown together into the top of the furnace, gradually descend, and the first operation to which the ore is subjected is reduction. Carbonic oxide gas arising from the combustion of