accurate observation of meteorological phenomena at the several military and naval posts, and that they report their proceedings at the next regular meeting of the Institution. Mr. Bulfinch, from the committee, made a report upon Mr. D'Arcy A. French's communication on grammar. Mr. Lawrence reported upon the Treasurer's accounts for the year 1841. Mr. Greenhow, from the Department of Astronomy and Natural Philosophy, reported: That the Department recommends for publication in the transactions of the So. ciety, the Meteorological Journal kept at the Observatory in Washington, by Lieut. Gilliss, for the months of September, October, and November, 1841; as, also the list of the observations of the mean declination of the magnetic needle, and the heights of the thermometer, and barometer, for each of the magnetic hours during July, August, September, October, November, and December, 1840, as observed by Lieut. Gilliss, at the observatory in Washington. That the Department having examined the letter addressed to the Institution, by Mr. J. H. Belcher, on the 10th January, 1842, and the accompanying memorial, "calling the attention of the Members of the House of Representatives of the 27th Congress to the great importance of a precise determination of the longitudes of the principal stations and posts in the United States," and recommending that Congress should order at a moderate expense, "the collection, reduction and gen. eral discussion of the observations now available for that purpose," reports: That although it fully concurs with the letter and memorial, as to the importance of having the longitudes of the principal cities, naval stations, and posts, in the United States accurately determined, it nevertheless conceives that any measures on the part of the Institution for the attainment of that object in the manner proposed by the letter and memorial, would be premature, inasmuch as observations have been and are now being made in different parts of the United States, under the direc. tion of the Navy Department, in connection with those also in progress by the officers and others in the squadron engaged in exploring the Pacific and Southern oceans, from all which observations, after they shall have been brought together, computations will be made, and the results published under the auspices of the Navy Department. These results will then be compared with each other, and with those obtained at the principal observatories in Europe, and there can be no doubt that the differences in longitude between the various points of observation on both sides of our continent, and in Europe, will be thus determined with much accuracy. Mr. Greenhow, from the same Department, made a report on Professor W. H. C. Bartlett's paper on Observatories. Mr. Markoe made the following report on the subject of Exchanges: The committee, consisting of Col. Abert, Mr. Markoe, Mr. Dayton, and Dr. King, appointed under a resolution passed at the stated meeting of the National Institution on the 13th December, 1841, which is in the following words: Resolved, That a committee of four members be appointed by the Chair to examine the subject of Exchanges, to propose a plan for that purpose, and to report fully thereon to the Institution for its further consideration and action, Beg leave, in pursuance of the directions of the said resolution, to report→→→ That the duty devolved on the committee by the resolution, is, First to examine the subject of exchanges; second, to propose a plan of exchanges; and, third, to report thereon to the Institution. In reference to the first point, viz: "the examination of the subject," the committee state, that they have examined the subject, and that the result has been a full conviction of mind that a system of exchanges is of very great importance in the accomplishment of one of the primary objects for which the National Institution has been declared to be formed, viz: "the establishment of a National Museum of Natural History," &c., &c. Exchanges enter essentially into the plan of every society constituted as the National Institution, and having like objects in view; and no occasion has been omitted to acquaint societies and individuals, whose correspondence has been sought by or offered to the National Institution, that a system of general exchanges would be entered upon as soon as the Institution should be able to mature a plan for that purpose. Under this assurance, and independently of it also, it should be added, valuable collections of various kinds have already been received by the Institution, which is thus already placed in a position which makes it incumbent on us to redeem the pledge that has been given. The committee consider it superfluous to dwell upon the advantages of exchanges; but they wish the members to know that for this object they have already in hands the most abundant materials-materials which are increasing and will continue to increase every day. These materials consist of contributions made by members, by individuals who are not members, by societies and institutions at home and abroad, and by foreign Governments, as well as of those accessions that have been made by the Exploring Expedition, which has already sent home an inexhaustible quantity and variety of duplicates. It is well known to the Institution that the collections received from all these sources are equally and absolutely the property of the Government, and that therefore the permission of the Government is indispensable to enable the Institution to part with the duplicates derived from all these sources. This permission, it is believed, will be cheerfully accorded. At the same time the committee, for obvious reasons, do not think it proper to ask the Government to allow the Institution to part with any of the duplicates of the Exploring Expedition, until the squadron shall have returned. In reference to the second point, viz: a plan of exchanges, the committee do not feel called upon or competent to enter into details. These must be left in a good degree to those whom the Institution may see fit to charge with the execution of the plan, in which of course they will be governed by the practice of other Institutions, and by such regulations as it may become expedient to adopt from time to time to suit our own convenience and peculiar circumstances. Here, however, on the threshold of the plan which the committee mean to propose, they regard it of consequence to suggest for the sanction of the Institution, that in exchanges of all kinds, the natural productions of our country shall first and always have a decided preference. A great and leading design of the National Institution is to explore and develop our own resources, and to study and describe the natural history of the United States. To this end our exertions must principally be directed. It should be the pride of all connected with or interested in a National Institution, to see every State in the Union fully represented in a National Cabinet, established at the seat of Government. This method, while it recommends itself to us and our interests, is calculated to extend benefits and encouragement to the societies and naturalists of our own country, who will thus have a central depository, from which they may enlarge and vary their own collections; and thus, also, in due time, the duplicates of the Exploring Expedition may, with the greatest advantage, be diffused through. out the land, thereby fulfilling, in the amplest manner, the intentions of those who projected, and justifying the liberality of the Government which sanctioned that noble project. With these preliminary remarks, and under the restrictions which are embraced in them, the committee recommend 1st. That a system of exchanges be entered upon without delay. 2d. That the Curator and assistants be directed, for this purpose, to separate all duplicates, except those from the Exploring Expedition; and that they select and label such specimens as are to be sent to individuals or societies. 3d. That the first step taken be to discharge the obligations of exchange already incurred by the Institution. 4th. That a committee be appointed, to whom the Curator shall submit all sets of specimens thus set aside for any given exchanges, who shall decide upon the equivalency, before said specimens shall be boxed up and sent off. 5th. That in all cases of difficulty which may arise, reference must be made to the President or Vice-President of the Institution for decision, who will, if they conceive it necessary, submit the question to the Institution. 6th. That a book be kept by the Curator, subject at all times to the inspection of the committee, in which must be noted the contents of each box or package; lists of the articles for which they are the equivalents; the name and place of the society or individual to whom one set is to be sent, and from whom the other has been received. In what the committee have now submitted, they conceive they have done all that it was possible or necessary to do at present, in reference to the third point of the resolution, viz: "reporting fully on the subject;" although they are perfectly sensible that in their report they have presented the subject in the most general manner, believing that experience and practice alone will enable the Institution gradually to settle upon a complete system. The committee beg leave to add, that the present report is not to be regarded as final, but that it is submitted, with all due deference to the Institution, to use the concluding words of the resolution, "for its further consideration and action." COMMUNICATIONS TO THE INSTITUTION. ON THE PRACTICAL DETERMINATION OF THE HEATING POWER OF FUEL: BY WALTER R. JOHNSON. In the progress of improvements in arts, navigation, and the application of heat to domestic purposes, questions of great interest present themselves for experi. mental determination. The new era in our Naval history which is about to commence with the introduction of war steamers, is a very suitable period to inquire into the relative values of those varieties of fuel which may be found available for the purposes of steam navigation. In various parts of the United States are found combustibles adapted to this purpose; but as yet their relative values, either as compared with each other or with the foreign mineral fuel so much used at present, have been but partially determined. In a work recently published relating to the use of anthracite in the manufacture of iron, I have given several tables of experiments conducted by different individuals, exhibiting the results of trials on a few varieties of anthracite and bituminous coals. The same work also contains a synopsis of what has been done in Europe towards determining this important question of the relative values of coals for the production of steam. It is proposed in this communication to present to the National Institution some few general results, to which the details contained in the above mentioned work appear to lead, and also to embrace a comparison with other results obtained with the same kinds of fuel. It may not be amiss to state that the method of determining the relative value of combustibles for the purpose of generating steam, consists in ascertaining the weight of water which can be converted into vapor by the combustion of a given weight of each variety of fuel. The method which has been often heretofore pursued, consisted in ascertaining the amount of the ultimate constituents of fuel, carbon, hydrogen, and oxygen, and computing the quantity of oxygen required to enter into combination in order to effect their complete combustion. Assuming that the quantity of heat afforded was directly proportionate to the quantity of oxygen consumed, the calculation of relative heating powers was made upon the admission, that the heating power of pure carbon had been determined, and that the power of other combustibles would be proportionate to the several quantities of oxygen which they would absorb. The experiments of Lavoisier, and more recently those of Despretz, have been relied on to give the heating power of pure charcoal. The latter fixed the quantity of water evaporated by the combustion of one pound of pure charcoal, obtained by the distillation of sugar at 12.3 pounds, taking the water at 32°, which is equiva. lent to 14.45 pounds, at the temperature of 212°. The experiments of Richardson and those of Regnault on coals, and the analysis of wood by Peterson and Shoedlen, have all had in view the determination by this theoretical means of the heating power of the several combustibles. Ingenious as this method certainly is, it has failed to give results which could be, generally, reproduced when a practical application was sought to be made of the information thus acquired. The practical commonly fell short of the calculated efficiency of fuel. In the practical determination of the value of fuel, the kind of evaporating vessel, the due regulation of the fire, the nature and condition of the products of combustion, the temperature of water used, and that of the air which supplies the grate, are all circumstances to be attentively considered. The hygrometin state of the fuel itself also deserves notice. From the tables in the treatise above referred to, from page 129 to page 142, are derived the following comparisons of results, deduced from the experiments of Dr. Samuel L. Dana, of Lowell, Massachusetts. 1. In plain Cylindrical Boilers, twenty feet long, thirty inches in diameter. Sydney coarse bituminous coal, 7.18, 208 pounds per hour burned. Philadelphia pea coal, 8.60, 180 pounds per hour, on an average. Philadelphia pea coal, mean of 10 days running, 9.48, 100 pounds per hour burned. 2. In Cylindrical Boilers, twenty feet long, forty-five inches in diameter. Coarse Sydney anthracite, 6.04, 300 pounds burned per hour. Anthracite dust, Sydney slack, 7.40, 233 pounds burned per hour. Anthracite dust, Sydney bituminous slack, 7.51, 228 pounds burned per hour. 3. In three Cylindrical Boilers, thirty-six feet long, twenty-four inches in diameter. 4. In four Cylindrical Boilers set on Mr. A. A. Hayes's plan, each twenty feet long and twenty-four inches in diameter. Sydney coal, screened from dust, 5.83, 250 pounds burned per hour. Sydney slack alone, 8.64, 1483 pounds burned per hour. Philadelphia poa coal alone, 9.06, 117 pounds burned per hour. Boston anthracite dust, Sydney slack, 9.60, 108 pounds burned per hour. Lackawanna nut anthracite, 9.77, 106 pounds burned per hour. Anthracite dust 3 parts, Sydney slack 1 part, 10.24, 141.5 pounds burned per hour. Anthracite dust 4. Sydney slack, 11.13, 112.5 pounds burned per hour. Anthracite dust 3, Sydney slack 4, 11.37, 107 pounds burned per hour, |