ART. XIV.-Notice of a new group of Eocene Shells; by IN dividing the Tertiary deposits into groups, according to difference of genera and species, it is objected by some naturalists that the diversity might be occasioned by a difference in depth of water at the same period of time. This and other causes originate a marked variation in the Miocene deposits of Maryland and Virginia, but the palæontologist is never in doubt of the relations of these Miocene localities. When, however, we find two beds in juxtaposition, the testacean groups of which differ entirely in species, and the evidence is clear that they must have lived and died in or near where they are now found, we are justified in giving each group a distinct name, and in supposing that they represent different periods of time. The strata at Vicksburg, Miss., as represented from the base at low water to the top of the Oligocene, decide a point of great importance in Tertiary geology. Neither Lyell, Ruffin, nor Tuomey, who all give a slight notice of Shell Bluff, on Savannah river, say anything of the age and relations of the large Ostrea Georgiana, so abundant there. Fortunately, at Vicksburg this shell occurs in the lower part of the bluff, below the Orbitolite limestone of the Jackson Group, associated with a distinct group of shells peculiar to a well-marked subdivision of Eocene strata. We know nothing from the geologists who have examined Shell Bluff of any species of shell associated with O. Georgiana; but at Vicksburg the species are well preserved, and are remarkable for having no affinity with species above or below them. I propose therefore to distinguish this assemblage of testacea by the name of the Shell Bluff group, the situation of which is in the Upper Eocene. There is no town near its outcrop other than Vicksburg by which its locality could be more precisely indicated, but it is only in Warren Co., Miss., that the group can be clearly defined by other fossils than Ostrea Georgiana. The following section will show the relative position of this group: VICKSBURG BLUFF. Calcareous silt with land shells of recent species,... Jackson Croup.-Orbitolite limestone. Shell-Bluff Group. Black lignite clay and gray sand with Ostrea Georgiana Conrad, Gray or biack lignitic clays and sands,. Solid lustrous lignite,... ART. XV.-Professor Treadwell's Improvements in constructing Cannon; Address of the President of the American Academy of Arts and Sciences (Prof. ASA GRAY) upon the presentation of the Rumford Medal to Professor TREADWELL, November 15, 1865. [Extr. from the Proceedings of the American Academy, vol. viii.] Ar the Anniversary Meeting last May, upon the unanimous recommendation of our Rumford Committee, the medal founded by Count Rumford was by the Academy awarded to Prof. Daniel Treadwell, for certain improvements in the management of heat. This medal is now before us. It is the first which the Academy has ever bestowed upon one of its immediate members. As your organ upon this occasion, before we place this testimonial in the hands of our distinguished associate, it is proper that I should briefly specify the grounds upon which your Committee proposed, and you made, this award. It is well understood, and the terms of the vote distinctly show, that this medal was awarded for an invention or an improvement in the management of heat. It is also well known that this particular improvement is a part,-the initial part, indeed,-of a series of inventions, applicable to other uses, no doubt,-but through which the character of ordnance has been changed, and its power immensely increased. This was the end and aim of the improvement for which the medal is given. We may, therefore, and we must upon this occasion, speak of this particular improvement in the management of heat in connection with the mechanical inventions which accompanied and followed it, and to which indeed the former is incidental. For the whole important series of mechanical inventions which I am to recapitulate, the Academy must regret that it has no honors. which it can bestow. But their history is upon our records, embodied in the communications addressed to us by their author from time to time; and we can only hope that the country and the world, when at length sensible of their obligations, may render the tardy meed of justice, if not of gratitude. In his earliest communication,-a pamphlet published in the year 1845,-Mr. Treadwell seems to think that the appropriateness of the term "useful," as applied to an improvement in implements of destruction, may be questioned. We need have no misgivings in this respect. So long as life and property, which the ravages of war destroy, are not the most valuable of human possessions, they may be justly yielded and taken, if need require, for the preservation of those that are. And so nations must always count among their greatest benefactors those whose AM. JOUR. SCI.-SECOND SERIES, VOL. XLI, No. 121.-JAN., 1866. inventions increase their strength and defense in war. And certainly those men who, by their inventive genius, revolutionize the art of war, exert a most powerful and enduring influence upon the fate of empires, the course of history, and the progress of civilization. We in our day, within the last fifteen years, have witnessed a change in the means of attack and defense greater than any made in the two hundred years previous, a change involving a complete revolution in tactics, both on land and on sea. To take a single illustration from heavy ordnance,-in which the importance of the change impresses us when we are told that our strongest forts, armed with the best guns we had ten years ago, could oppose no effectual resistance to the entrance of such ships as are now built into any of our harbors; and that a ship could now be built and armed, which, singly, would overmatch our whole navy as it was in 1855. Fortunately, the balance is redressed by equal improvement in defense. The improvement in fire-arms, both great and small, is in their increased range and precision. When the effective range of a musket-bullet was extended from 200 yards to 1400 or more, it became imperatively necessary that ordnance should be improved in the same ratio, or it would be useless, as gunners and horses would be picked off by small arms long before they could effectively reach the enemy. This improvement in guns of great calibre has been made, with consequences the importance of which, present and prospective, cannot be overestimated. But the point which we have to consider is, that this increased range and precision are entirely dependent on the augmented strength of the gun. The weakness of the gun is the only thing that imposes a limit to the range, short of the absolute strength of the explosive material used. It is the strength of the gun which not only gives the range, but makes rifling possible, with precision and all the advantages of elongated shot. All inventions relating to the different modes of rifling, the form of the projectile, and the devices for breech-loading, are necessarily subordinate to the question of strength with this sufficient, those become simple problems, to be rapidly determined by the ingenuity of many inventors. Now the limit of strength of cast-iron and of bronze cannon had long ago been reached. Excepting Captain Rodman's improvement, and certain modern advantages in working and casting metals, no material advantages had been gained over guns cast in the reign of Queen Elizabeth. But the most effective guns of the present day embody new principles of strength. They are all built-up guns. With them are associated the names of Armstrong, Blakely, Whitworth, Parrott and others. Whatever may be the relative merits of these several varieties, our interest is confined to the question of their strength, that is, to the principles of their construction which have made them stronger than common guns, and rendered their respective subordinate improvements possible. These principles are two, and their introduction at different times into the manufacture of cannon constitutes two successive steps, and the only steps, which give distinctive character to the guns under consideration. Both originated with Mr. Treadwell. These two inventions are often confounded, although more than ten years elapsed between them. The confusion is doubtless owing in some degree to the fact that the two are found combined in nearly all the modern built-up guns. The first initiated a system of construction which may be designated as the coil system; the second, what may be named the hoop system. The first was successfully applied to the making of cannon by Mr. Treadwell in the year 1842, and a full account of it was published in 1845; the gist of the invention being in so constructing the gun that the fibres of the material shall be directed around the axis of the calibre. This method of construction is described in Prof. Treadwell's own language as follows: "Between the years 1841 and 1845 I made upwards of twenty cannon of this material [wrought iron]. They were all made up of rings, or short hollow cylinders, welded together end wise; each ring was made of bars wound upon an arbor spirally, like winding a ribbon upon a block, and, being welded, and shaped in dies, were joined endwise when in the furnace at a welding heat, and afterwards pressed together in a mould by a hydrostatic press of 1000 tons' force. Finding in the early stage of the manufacture that the softness of the wrought iron was a serious defect, I formed those made afterwards with a lining of steel, the wrought iron bars being wound upon a previously formed steel ring. Eight of these guns were 6-pounders of the common United States bronze pattern, and eleven were 32-pounders of about 80 inches' length of bore and 1900 pounds' weight." The soundness and value of this principle of construction were fully confirmed in England by the experiments of Sir William Armstrong in 1855, and attested by his evidence before a committee of the House of Commons in 1863. He there describes his own gun as one "with a steel tube surrounded with coiled cylinders,"-as "peculiar in being mainly composed of tubes, or pipes, or cylinders, formed by coiling spirally long bars of iron into tubes and welding them on the edges, as is done in gun-barrels." His indirect testimony to the originality of Mr. Treadwell's process is equally clear; viz; that, within his knowledge, no cannon had ever been made upon this principle until he made his own in 1855,-he being, as we must suppose, ignorant of what Mr. Treadwell had done thirteen years before. The statement of Mr. Anderson (witness before the Commons' Select Committee), made before the Institute of Civil Engineers in 1860, is equally explicit as to the nature and value of this method. of constructing cannon. And, finally, the high estimate of its importance abroad is shown not only by the honors and emoluments conferred by the British government on the re-inventor, but still more by the actual adoption of this gun as the most ef ficient arm yet produced. For it must be borne in mind that the faults or failures, complete or partial, of the Armstrong and similar guns, are not of the cannon itself, as originally constructed, but of breech-loading contrivances, of the lead coating of the projectile, or of other subsidiary matters. That our colleague's original invention, the value of which is now so clearly established, should have been so generally unacknowledged by inventors abroad is his misfortune, not his fault. For, not only were his guns made and tested here, and their strength as clearly demonstrated before 1845 as they have been since, not only was a full account of the process and of the results published here in that year, but a French translation of his pamphlet was published in Paris, in 1848, by a professor in the school of artillery at Vincennes, and Mr. Treadwell's patent, with full specifications, was published in England before Sir William Armstrong began his experiments. The difficulties to be overcome in making such a gun,-great at all times, as Sir William Armstrong and Mr. Anderson testify, were far greater in 1842 than in 1863. These difficulties were mainly, if not wholly, in welding large masses of wrought iron in the shape of tubes or cylinders. It is for overcoming these difficulties that this medal is bestowed, and especially for the means and appliances by which this difficult mechanical achievement was effected in the furnace "by the agency of fire." An incidental but noteworthy part of the improvement was the welding by hydrostatic pressure, an operation which is just now coming into use in England, but has not yet attracted attention in this country. We come now to the second improvement in the construction of artillery, the invention of the hooped gun. This is not always clearly distinguished, even by those occupied with the subject, from the gun formed of coiled rings. But a simple statement will bring into view distinctly the new principle of strength here introduced. If an elastic hollow cylinder be subjected to internal fluid pressure, the successive cylindrical layers of the material composing it, counting from within outwards, will be unequally distended, and the resisting efficiency of the outer layer will be less |