general orographic condition of Texas; 2. General geognostic constitution of the country; 3. Diluvial and alluvial formations; 4. Tertiary formations; 5. Older or Palæozoic strata; and 6. Plutonic rocks.

The principal part of the volume is devoted to a geological description of the chalk formation of Texas, with an enumeration and description of its organic remains, which occupy eighty-eight pages of the volume. These are followed by descriptions of Palæozoic fossils, and of three species of fossil wood from the tertiary.

The cretaceous fossils figured occupy ten quarto plates, and number one hundred and twenty-four. Of these one hundred and one are new or yet undetermined species, and twenty-three are identical with species previously known. These are beautifully illustrated. The Paleozoic fossils number ten species, of which eight are new. These are chiefly of the carboniferous period, and we recognize them as forms which prevail farther to the north and west in the same formation. The three species of fossil wood from the tertiary, described by Unger are Sillimania Texana, Roemeria Americana, and Thuyoxylon Americanum.

The fossils here described and figured, had been already indicated in Dr. Roemer's previous work on Texas.*

The present work offers a very valuable accession to our knowledge of the American Cretaceous formation; contributing more species of fossils than have been published since the appearance of Dr. Morton's Synopsis in 1830: Dr. Roemer has given some valuable observations on the climatic influences upon the fauna of the chalk period, and has instituted comparisons between this formation in Texas and other parts of America, as well as with the same formation in Europe.

On comparing these figures of Texan cretaceous species with collections from Nebraska, a few degrees farther north, we are struck with their almost total dissimilarity. In the little which we already know of it, we have but a foreshadowing of what is yet in store for us when this formation, which extends from the Tropic of Cancer to the 48th degree of latitude, shall have been completely explored.

H.

13. Geological Map of Keweenaw Point, Lake Superior, Michigan; by J. D. WHITNEY, assisted by S. W. HILL and W. H. STEVENS.This is a large pocket map of the Lake Superior Mining Region, 2 feet by 4 in its dimensions. It gives an admirable view of the Geological structure of the region, and is excellent in illustration of an article in this volume from the Report of Messrs. Whitney and Foster. The different rocks are indicated as usual by colors, and many facts of great geological interest are indicated by their arrangement, and the positions of the various metallic veins which intersect them. The map contains also a section across Keweenaw Point by Copper Falls and Northwestern Mines. It is invaluable to geological science as well as to the topographer and traveller.

14. People's Journal; Vol. I, Nos. 1 and 2, November and December, 1853. 32 pp. large 8vo.-This new popular monthly opens with an article on Willison's Hand Thrashing Machine. The Journal is de

*Texas: mit besonderer Rucksicht auf deutsche Auswanderung und die physicalischen Verhältnisse des Landes nach eigener Beobachtung geschildert; von Ferdinand Roemer. Mit einen naturwissenschaftlichen Anhange und einer topographische-geognostischen Karte von Texas. Bonn, bei A. Marcus, 1849.

voted to Farming, Agriculture, Horticulture, Mechanics, and practical science, and is very fully and handsomely illustrated with cuis representing machinery, implements of husbandry, fruit, cattle, plans of buildings, the National Exhibition of Horses at Springfield, American steamships, etc. No. 2 contains 72 wood-cuts, some of them illustrating im portant inventions at the Crystal Palace. Price 50 cts. each 6 months.

E. HITCHCOCK, D.D.: Outline of the Geology of the Globe, and of the United States in particular; with two Geological Maps and sketches of characteristic American Fossils. 8vo. pp. 138. Plates. Boston, 1853. Phillips, Sampson & Cɔ.

THOMAS COLE, A.M.: List of Infusorial Objects, found chiefly in the neighborhood of Salem, Massachusetts, with a sketch of the progress of this brauch of Natural History. From the Proceedings of the Essex Institute. 18 pp. 8vo. Salem, 1853. MAGNETICAL AND METEOROLOGICAL OBSERVATIONS AT TORONTO, IN 1843, 1844, 1845, printed by order of her Majesty's Government, under the superintendance of Col. Edward Sabine. 640 pp. 4to. London, 1853.

B. STUDER: Geologie der Schweiz (Geology of Switzerland), in 2 vols. 12mo. Berne an Zurich, 1853.

E. F. KELAART, M.D.: Prodromus Fauna Ceylonica. 198 and 62 pp. 8vo. Ceylon, 1852.-Treats with considerable detail, of the Mammalia and Reptiles of Ceylon. ANNALES DE L'Observatoire PHYSIQUE CENTRAL de Russie, Parts 1 and 2 for 1830. 808 and 250 pp. 4to. St. Petersburg, 1853.

COMPTE-RENDU ANNUEL addressé à S. Exc. M. de Brock, Min. des Finances, par le directeur de l'Observatoire Physique Central, A. T. Kupffer, année 1852. 72 pp. 4to. St. Petersburg, 1853.

C. F. RAMMELSBERG: Fünftes Supplement zu dem Handwörterbuch der chemischen Theils der Mineralogie. 270 pp. 8vo. Berlin, 1853.

C. F. NAUMANN: Anfangsgründe der Krystallographie, 2nd Edition. 292 pp. Syo. Leipzig, 1854.

LIEBIG AND KOPP: Jahresberichte for 1852. Parts I and II.

PROCEEDINGS ACAD. NAT. SCI. PHILADELPHIA, vol. vi, No. 10.-p. 375. Note on Cambarus Gambelii; Agassiz.—p. 377. Note on Cetaceau remains in the U. States; Leidy. p. 378. New Rana and Bufo; Baird-p. 379. On Thala; Genth-p. 380. A new Salmo; C. Girard.-Note on Cambarus Gambelii; Girard.--p. 381. Notes on the Ornithology of Wisconsin; P. R. Hoy. p. 386. On the American species of Esox; C. Girard.-p. 387. New species of Fish collected by J. H. Clark on the U. S. and Mexican Boun lary Commission; Baird and Girard.-p. 390. New Arkansas fishes; Baird and Girard-Note on Nebraska Mammalian and Chelonia Fossils; Leid-No. 11.-p. 395. Catalogue of Birds of Ohio; N. C. Read-p. 402. New species of Pacane Nut; J. Le Conte.--p. 404. Three new American Arvicole, and remarks on other Ro lents; p. 415. On Crotalus durissus and C. adamanteus; J. Le Conte.--p. 420. New Reptiles of the Exploring Expedition under C. Wilkes; C. Girard.--p. 425. Notes on the Ornithology of Wisconsin; P. R. Hoy.--p. 430. New species of Diatomaceæ, collected by U. S. Exploring Expedition under C. Wilkes; W. H. Harvey and J. W. Bailey.

Works received from the Publisher:

Vindiciae Plinianæ, scripsit C. L. URLICHS. Fasc. I. Gryphiæ, 1853. In Libr. C. A. Kochiana, Th. Kunike.

De Pandora; Commentatio Mythologica, scripsit G. F. SCHOEMANN. Gryphiæ, 1853. In. Lib. C. A. Kochiana.

Leonhard Euler's Theorie der Bewegung fester oder starrer Körper mit Anmerkungen und Erläuterungen, herausgegeben von J. PH. WOLFERS. Dr. und Professor. 1st and 2nd parts. Greifswald, 1853. C. A. Koch's Verlagsbuchhandlung.

Ueber die prätorischen Ju licialstipulationen mit besonderer Berucksichtigung der stipulatio judicatum solvi. Eine rechtshistorische Abhandlung von Dr. J. TH. SCHIRMER, Docenten der Rechte zu Breslau. Greifswald, 1853. C. A. Koch's Verlagsb.

Die unter Xenophons Namen überlieferte Schrift vom Staate der Lacedämonier und die Panathenaische Rede des Isokrates in ihrem gegenseitigen Verhaltnisse dargestellt von RUDOLF LEHMANN. Greifswald, 1853. C. A. Koch's Verlagsb.

Kritische Skizzen zur Vorgeschichte des zweiten punischen Krieges; von Dr. Franz Susemihil. Greifswald.

THE

AMERICAN

JOURNAL OF SCIENCE AND ARTS.

[SECOND SERIES.]

ART. XII.-On the Elastic Force of Heated Air, considered as a Motive Power; by FREDERICK A. P. BARNARD, Professor of Chemistry and Natural History in the University of Alabama.

In the discussions which have recently taken place with regard to the power, economy and value of hot-air engines, the attention of all who have participated in them appears to have been exclusively directed to the advantages and disadvantages presented by a particular case. The question seems not to have been contemplated in its more general aspect; or rather it seems to have been assumed that there exists no general question which the success or failure of this particular experiment will not settle. Those who are satisfied that the engines of Capt. Ericsson cannot succeed, seem ready at the same time to conclude that no engine whatever can be successful which proposes to derive its power from the same source. Experiment may prove this conclusion to be correct; but if so, it will have to be recorded as a fact in scientific history no less remarkable than true, that all those dis⚫tinguished men whose labors in this branch of science have illustrated the present age, and have built up the entire theory of caloric as it is now received, have been completely in error in regard to one of their most important practical inferences, deduced from the careful study of years.

Thompson, Rankine, Joule and Regnault have all expressed the opinion that an air engine may be constructed which shall be SECOND SERIES, Vol. XVII, No. 50.-March, 1854.

20

economically much superior to the steam engine.* One of these, Mr. Joule, has even published an outline of a plan which he would adopt in order to secure the advantages to be attained by the use of this motive power;† and he has shown, by the application of the convenient formula of Prof. Thompson, for determining what fraction of the heat expended is converted into power by thermo-dynamic engines, that an engine constructed on his plan would produce an amount of mechanical effect greater in the ratio of 6 to 5 than a condensing steam engine with fourteen atmospheres of pressure in the boiler, and in which the steam expands itself in the cylinder to the temperature of 80°. Compared with steam expanding in like manner from the pressure of five atmospheres, the economy would be nearly as 3 to 2; and taking the steam at the original pressure of two atmospheres it would be almost as 2 to 1 (1:18). But in these computations, the expansion of steam in the cylinder is presumed to carry the temperature down to 80°, a condition never fulfilled in practice in any steam engine. Comparing this proposed engine of Mr. Joule with a steam engine in which the expansion in the cylinder is from five atmospheres to one, as in the ordinary noncondensing engines, the result would be favorable to the air engine as 3 to 1. And if we compare it with a non-condensing engine at two atmospheres, we shall find that the air engine would be eight times and upward superior to the other in point of economy.

In all the discussions which the engines of Capt. Ericsson have provoked, certain propositions, which are rendered true by the peculiarities of those engines, have been tacitly assumed to be true universally; while, nevertheless, they express only the necessities of that particular case. Such are the following, viz:

1. That the available power of air engines is restricted within narrow limits by the resistance of the supply cylinders.

2. That the economy of heat in such engines is to be measured by the degree of thoroughness with which the regenerators do their work; and is therefore greatly affected by the incompleteness of the transfer of heat, both ways, between them and the air.

3. That as the first condition foregoing requires a pressure above that of the atmosphere to be carried up to the end of the stroke, there must, in the nature of things, be a great waste of heat, by the expansion of the emergent air.

*This is the important point. The air engine need not stand condemned because it will not (if it will not) drive a Collins liner. The distrust with which its prospects seem to be at present regarded, has grown mainly out of the attempt to make it accomplish labor to which it may possibly hot be adapted. Air engines may always be too bulky and too ponderous to be well suited to rapid locomotion: but they may nevertheless be employed to great advantage in driving machinery or serving generally as stationary powers.

† Lond. and Ed. Phil. Mag., Jan., 1853; and Phil. Trans., 1852, Part I.

4. That a very large additional waste must occur through chimneys and flues, and by radiation from the cylinders.

5. That the leakage must be enormous, as compared with what occurs in engines driven by steam.

6. And finally, that air cannot be heated in such quantity, with such rapidity, and to such a degree as the exigencies of the case require.

Not one of these propositions is necessarily or universally true; and it will presently be seen that the plan of Mr. Joule is in defiance of all of them. On the other hand, it must be admitted that there are some disadvantages quite inseparable from all air engines of whatever description. It is certainly true,

1. That the mean effective pressure must, in the case of every such engine, be moderate compared with the absolute tension of the air in the cylinders.

2. That the mean effective pressure, if the engine is worked strictly with a view to economy, bears a less ratio to the absolute pressure, than it might do with less economical arrangements.

3. That a large apparatus is necessary for the development of high power, even though the power be obtained economically.

4. That the highest economy requires so large expansion of the air in the working cylinder, as to make the counteracting pressure in the supply cylinder a great inconvenience, though not an insuperable difficulty.

Professor Thompson, of Glasgow, has shown that the fractional portion of the heat which in any thermo-dynamic engine is converted into force, is represented by the range of temperature through which the elastic fluid is cooled by its expansion, divided by the maximum temperature as measured from the absolute zero (459° below the zero of Fahrenheit).* It follows that, in order to apply the force of heated air economically, there must either be large expansion in the working cylinder, or the heat remaining in the air at its discharge must be absorbed by some contrivance like Ericsson's regenerator, to be afterwards employed again. Such a contrivance, apart from its necessarily imperfect absorbing power, has the disadvantage of being confined in its usefulness within rather narrow limits. Of these limits, the upper one is the temperature required to maintain the rarefied air, at its discharge, at the pressure of the atmosphere; and the lower is the temperature produced by compression in the supply cylinders. As the pressure increases, these limits approach each other; and it is quite evident that when they meet, the regenerator becomes, not only practically but theoretically, useless.†

* As to the strict applicability of this formula to the air engine, see a note below. It is a curious fact that these two limits meet at precisely the pressure which (with a given supply cylinder) makes the power of the engine a maximum. For if (adopting the symbols introduced further on, and those of a former article) we