Philadelphia pea coal, Sydney slack, 11.48, 100 pounds burned per hour. 5. In a tubular Boiler, thirty-six feet long, twelve tubes, each three inches in diameter. Coarse Lackawanna anthracite, 11.96, 85.8 pounds burned per hour. 6. In a Cornish Boiler of the usual construction, thirty-six feet long, six feet exterior, and three feet ten inches interior diameter. Coarse Sydney bituminous coal, 6.32, 233† pounds burned per hour. 7. In an improved Cornish Boiler, with three interior boilers inserted in the interior Flue. Coarse anthracite, kind uncertain, 10.90, 171.6 pounds burned per hour. Pea anthracite 3 parts, bituminous slack 1 part, 12.08, 136.6 pounds burned per hour. Lackawanna anthracite, ordinary size, 12.98, 145 pounds burned per hour. The following results have been obtained in this country, in a Locomotive boiler of the common form: Schuylkill anthracite, 9.51, 57.3 pounds burned per hour. Mr. Thomas Wicksteed has published a set of results obtained in Cornish boilers, using various sorts of fuel, which I have reduced to the standard of 212°, to render them comparable with the preceding and following sets. Unfortunately they have not come to hand with the rates of combustion annexed; but they may be arranged in the following order: Blythe Maine Northumberland bituminous coal, 7.44. Large New-Castle coal, average 8.64. Derbyshire, small New-Castle, 8.69. Welsh, New-Castle, 8.86. Gas coke, small New-Castle, 8.91. Gas coke alone, 8.92. Average Welsh, 8.98. Average small New-Castle, 9.01. Best small New-Castle, 9.38. Best Welsh coal, 10.71. In the work on Anthracite Iron, above mentioned, will be found at page 149, the following table of the evaporative powers of different kinds of fuel, as given by experience in different forms of boilers. 1. In a Locomotive Boiler. Bituminous coal, by N. Wood's experiments, 5.12. 2. In Wagon Boilers. New-Castle bituminous coal, by Watts's trials, 9.63. 3. In Cornish Boilers. Welsh coal, trial by Henwood, 11.62. Welsh coal, experiments cited by Henwood, 11.78. 4. In a Marine Boiler on board the Steamer African. Heaton bituminous coal, 8.15. 5. In four Cylindrical Boilers on Hayes's plan. Anthracite, bituminous dust, 11.83. 6. In a plain High Pressure Boiler. Scotch bituminous coal, by Pigfe, 7.74. Anthracite, kind uncertain, 10.10. 7. In Player's Boiler for using Anthracite. Anthracite, by Schaufbautl's trials, 12.40. Anthracite by Parke's and Mauley's trials, 13.25. 8. In Dana's improved Cornish Boilers, newly altered. Anthracite of Beaver meadow, 15.56. Anthracite of Beaver meadow, maximum of Dr. Dana's results, 16.64. Though important general conclusions can be derived from the foregoing facts, yet, as several circumstances highly necessary to render the results comparable, have been very various in the several experiments, it is evident that we yet want an extensive series of operations on the several varieties, made in a manner which shall render them true indices of the heating powers of the several kinds of coal. PLAN OF EXCHANGES SUBMITTED BY DR. E. FOREMAN, OF BALTIMORE. The subject of exchanging specimens of natural history having been already forced upon the attention of the National Institution, I take the liberty to submit a few considerations, being the outlines of a plan which I have found to yield profitable results in my own practice. The necessity of repaying those naturalists who have contributed native or other species to the cabinet is obvious, and equally so the advantages to be derived by distributing the great numbers of the same species, which the Institution has accumulated and will continue to accumulate. Hav. ing studied the subject of conchology for a few years, in a private way, in the leisure time afforded by a long college summer vacation, and acting under the desire and for the purpose of enlarging my collections, I adopted a system by which I believe that the expenditure of time, money, and exertion, will yield the greatest results. The singular tribes of animals studied by the conchologist, are known to be extensively spread over every part of the globe visited by man, and that they likewise affect some situations in greater numbers, size, and variety of species, than others. In those countries whose zoology has been more fully explored than our own, as France, Germany, and England, it has been ascertained that soil and climate are the two great causes which modify their distribution. In reference to the first cause, limestone rocks and the superincumbent soil seem to be more favorable than any others, to the number and propagation of species. The next more favorable are the sandstones; basalt, granite, argillaceous, and slaty rocks, generally exercising a negative or unfavorable influence. The latter cause, climate, produces an unquestionable diminution in the number, size, and variety of species, bearing a general proportion to the lowness of the temperature, since, as we advance northward, many species disappear altogether. In temperate situations, individual species multiply to greater extent, and in warm districts they display a greater superiority in respect to color. Sheltered vallies, places of low elevation, with a southern exposure and a proximity to the sea-coast, afford the greatest advantages for the propagation of these tribes. Guided by these or similar views, the surface of the United States may be divided into a number of regions or districts, for the purpose of collecting its shells, and from each, as the soil or climate varies, we must expect to receive suites of specimens differing widely from each other. That we may assign some general limits to these portions of country, it will be necessary, first, to sketch out a few grand divisions, to be subdivided afterwards. If we travel, for instance, from the Atlantic ocean towards the great lakes, there will successively occur several marked lines or belts of country where the species must be changed to suit the soil, climate, elevation, temperature, and the salt or fresh condition of the water. In the sea, there will be found, and there may be dredged from the sub-merged coast, such as are peculiar to the sea, and may be designated as marine species. At the mouths of rivers and estuaries, and in the brackish water, which extends as far inland as the tide flows, another suite of species, peculiar to this combination of circumstances, will be detected. Beyond the point of high tide the water remains fresh, and here are found those which are known and designated as fluviatile species. Of the terrestrial species, a diversity equally striking may be noticed, by returning to the edge of the ocean, collecting all the species inhabiting the low flat lands, composed of sandy and clayey soil, extending, for the most part, along the whole coast of the United States. Compare these with such as inhabit the sides and summits of the low ranges of hills or terraces constituting the head of tide, and a striking difference will be at once perceived. These again are, in many respects, dissimilar from those living on the broad belt of the tertiary formations, which stretch along the base of the eastern slope of the primary Atlantic chain of mountains. Upon the sides and summits of these, again we discover new genera and species; and we notice, with surprise, that those which abound on the eastern slope, in but few cases cross over the ridge to the other or western aspect of the same chain. The most remarkable difference takes place, however, in the fresh water bivalves, especially of the genus unio, which becomes suddenly changed, from an elongated form and very thin shell, to swarms of new species, of great size, endless variety of form, and of astonishing thickness. These characteristics are maintained through. out the entire valley of the Mississippi. By pursuing our course still farther, we eventually come to a new zoological district, where great bodies of fresh water expand themselves like inland seas, inhabited, in many respects, by a different suite of species, and this may be known as the lake region. To effect a subdivision of these broad ranges of territory, we may cross them by any number of parallel lines, equidistant, as the parallels of latitude, and thus, in a rough way, assign the boundary to each smaller district. A great number of localities, whose natural history it were desirable fully to explore, will be created, and collections made within their limits will exhibit great dissimilarity of species, and frequently of entire genera. But in the unsettled, and, so far as science is concerned, the uncivilized state of many of the indicated regions, it were impracticable entirely to accomplish so desirable an end; for it would be a long time before an individual, disposed to collect and exchange species, could be found in each, and be placed in correspondence with the National Institution; and in its recent state, its duplicates, although exceedingly abundant, would scarcely afford a supply to so great a number. I have arranged the surface of the territory of the United States into these numerous por. tions, only to show that collections must be made from all of them, if we wish to possess complete suites of its shells. As an illustration of these principles, applied to practice, I established a correspondence with gentlemen in the various cities and towns on the Atlantic coast, to wit: St. John's, New-Brunswick; Portland, Maine; Boston, Massachusetts; a point a few miles north of Chesapeake Bay; Charleston, South-Carolina; Savannah, Georgia; and Mobile, Alabama. I proposed to accomplish, by this method, a collection of our coast shells, and have mainly succeeded. But it will strike every one who runs his eye along a map of the coast, that there are, by this enumeration, great gaps left unfilled. I have no station on Long-Island or the Jersey coast; both sides of the peninsula of Florida are unrepresented; and it were desirable to have collections from the mouths of the Mississippi. For the interior, I have selected, at the head of tide, corresponding points to the above; likewise in the valley of the Mississippi, and others on the Ohio, Cumberland, and Tennessee rivers. My experience leads me to believe that the species native to this country will be more acceptable, generally, to intelligent correspondents, than such as may be procured from foreign voyages, unless the latter be very rare, and in fine preservation.. I have uniformly preferred holding correspondence with teachers or professors in various colleges, or with professional men, who, by their position in society, are above the reach of the invariable cui bono interrogatory; since many well-meaning persons hold the study of these portions of science, without regard to their direct or indirect utility, in great contempt, and this deters many private persons from their pursuit. Such correspondents likewise command an influence over many persons in their respective districts, and are enabled to draw from all quarters, by a little exertion, large supplies of various new and old species. Another advantage still is found in procuring immediate and full returns from such, as, for the most part, they have access to either public or private cabinets, know how to collect in the field, and no time is lost in the process of initiation, which ordinarily occupies one or two seasons before the haunts of all the species become familiar. In adopting this system and setting it to work in a thinly populated country, in which, for the most part, reliance must be placed on uninformed agents, it will be absolutely necessary to issue very minute instructions, to be observed by the collector, that they may, with the least expenditure of time, do the best possible with the country they live in. More especially every inducement should be held out to all correspondents to send in wet preparations of the animals which occupy the shells, and dissection of parts, illustrative of their anatomy, preserved in spirits. If the National Institution could succeed in establishing branch institutions in the various quarters indicated above, a measure which I would urge upon the early attention of the members, the harvest of species waiting to be gathered in would be accomplished so much the more speedily. Respecting the willingness of gentlemen, especially those to whom I have referred, to undertake exchanges, I take this opportunity to bear testimony to the great liberality and promptitude which I have invariably found to actuate naturalists, though personally strangers to each other. I have attributed these noble qualities as much to the gentle influences exercised by their quiet pursuits, as the wish to extend the humanizing results which always attend the cultivation of science. WASHINGTON UNIVERSITY OF BALTIMORE, Dec. 10, 1841. OBSERVATIONS ON A PORTION OF THE ATLANTIC TERTIARY REGION, WITH A DESCRIPTION OF NEW SPECIES OF ORGANIC REMAINS: BY T. A. CONRAD. Several circumstances combine to give interest and importance to the tertiary deposits of the Atlantic coast of the Union. These chiefly consist in variations from the usual characteristics of European tertiaries. The first which I shall notice is the remarkable connection of secondary with tertiary, or cretaceous with eocene deposits, by means of the following fossils, which I discovered in a tour in the Southern States in 1832, '33 viz: Nummulites Mantelli, (nob;) Gryphœa vomer, (Morton;) Plagiostoma dumosum, (Morton.) The white limestone of Alabama, which contains these fossils, is connected with the greensand formation of New-Jersey, by three species of shells: Ostrea panda, Ostrea cretacea, and Gryphæa vomer, (Ostrea lateralis, Nillson.) The second important disagreement with foreign tertiaries is the absence of any trace of fluviatile remains. The Gnathodon, a bivalve inhabiting estuaries where the water is scarcely saline, and fresh during the inundations of the rivers, is the only evidence, hitherto obtained, of the occurrence of fresh water streams-a remarkable fact, considering the great extent of land which evidently was present in the tertiary periods. The third peculiarity of the American tertiaries is the abrupt line of demarcation between the fossil groups which they contain; show. ing no gradual passage or interchange of forms, although the relative levels, above the sea, are of no important variation among the three divisions into which I have grouped the tertiaries, for a convenient but temporary purpose. No one, I presume, would refer this wide difference of zoological character to any relative condition of sea or land, caused by earthquakes, or by an elevation of the beds above |