As we have stated in a previous number, this respectable Association, after a two years' recess, met at Cleveland, Ohio, on the 28th of last month, and continued in session for five days, then adjourned after deciding upon the meeting in the city of Washington, D. C, in May next year. We will now present an abstract of the most practical interesting papers, and finish the same with this volume of the Scientific American. Prof. Pierce, of Cambridge, Mass., President of the Association organized the meeting and delivered a very neat and appropriate address. He said:— " We are again met in the service of a high cause ; after the unusual interval of two years we have again come together at an appointed rendezvous, t- make each other glad with the tidings of truth which we bring from the heavens and the earth, and to reanimate our fainting zeal by the story of the successful search for the philosopher's stone, the true elixir vitae, the fruit of tht tree of knowledge, and the footprints of Him to whom the earth is a footstool. Gentlemen, we are not convened for a light duty. Our self-imposed task is not an amusing child's play, arid we have not accepted the liberally offered hospitalities of this beautiful city for the enjoyment of a social &sHval. We have come to give and to receive instruction and inspiration. Gentlemen, we have come to study our duty as scientific men, and especially as American scientific men. We are to learn the apparent and not very pleasant paradox that America cannot keep pace with Europe in science, except by going ahead of her. The New World must begin to build upon a level above that of the Old World, and it must build from its own materials. This is not asking too much. It is no more than was accomplished by the American Ship and the American Reaping Machine. The Yankee who picked the hardest lock in England, and contrived a lock which all England could not pick, is but a type of American intellect. This was a work of mind, and we have a right to expect equal excellence in higher and more abstract efforts of American genius. But above all things it is not to be forgotten that the temple of science, by whomsoever built, belongs to no country or clime. It is the World's Temple, and all men are free of communion. Let us not mar its beauty by writing our names upon its walls. The stone which we have inserted is not ours ; it is not thine, it is not mine, but it is part of the temple. Let us not presume to make these walls resound with the bickerings of angry contention for superior distinction, and the foul complaints of mortified vanity. Let us not raise the money-changers' cry of mine acd thine,' lest the purifier come, and taking the royal jewel into his own possession, thrust us out into the ditch, and turn our fame into infamy. It has been observed by others not of our own number, that the meetings of the Association have been characterized by a generous appreciation of each other's labors. But mutual admiration is not our only or our most necessary office. Mutual criticism is equally imperative and equally conducive to the best interests of the Association. We must not permit erroneous statements to pass unchallenged. It is our stern and solemn duty to criticise and expose all false developments, whether they are intended, or the unintentional results of carelessness or ignorance. SATURN'S RING.—Prof. Pierce then proceeded to make some remarks on the ring of Saturn, confirmatory of his investigations on this subject, laid before the Association in 1851. The opinion adopted is, that the ring is a fluid. He said he had now the pleasure of confirming the impressions he then held, condemnatory of the theory advanced by La Place. We quote a passage from his remarks at Cincinnati:— " The author of the ' Mecanique Celeste ' proved that Saturn's Ring, regarded as solid, would not be sustained about the primary, unless it had decided irregularities in its structure. But the observations of Herschel and others have failed to detect any indications of such irregularity, and a laborious series of observations have finally convinced Mr. Bond of the utter impracticability of any important irregularities, and he has, therefore adopted the conclusion that Saturn's Ring is not solid, but fluid. * * * * I !m now convinced there is no conceivable torm of irregularity, and no combination of irregularities, consistent with an actual ring, which would permit tl.j ring to be permanently maintained by the primary if it were solid. Hence it follows, independently of observat;on, that Saturn's Ring is not solid." LITHOGRAPHY.—A paper of which the following is an abstract, was read on this subject by Lieut. E. B. Hunt, TJ. S. N. This art was discovered by Aloys Senefelder, in 1799, only 54 years ago. By the labors of D'Offen-bach, DeLasteyrie, Engelmann, Ackerman, Lemercier, and others, the iniant art, in being propagated from Munich, its birth-place, has also been much improved in many of its details, and has had some important extensions of its sphere of usefulness and capacity. De-Lasteyrie's autographic printing and Engel-mann's printing in colors, were great expansions of Senefelder's invention, while the excel1 mt .management of landscape and scenic, effects in Ackerman's establishment in London demonstrated a new capacity of the art. Of all artistic inventions none has so eminent a capacity for being abused as Lithography. In thoroughly skilbul hands, it has the capacity for producing effects of a high order, and some which are peculiar felicities of this art alone. But that this result may be attained, it is indispensable that labor, care, and skill, and indeed all the elements of any excellent art, should conspire. The artist needs to be such in fact, as well as in name, and the printer must posspis appreciation of the subject printed, and a technical mastery of his business, such as is quite too rare, especially among us. Lithography owes not only its existence but its possibility to the fact that several quarries, in the vicinity of Munich, furnish slabs of a limestone unform in texture, apparently compact, yet really having a somewhat open grain. Though other localities furnish stones which could be used, the real commerce of lithographic slabs is limited to the Bavarian quarries, especially Poppenheim and Sonnhofel. These furnish stones of ordinary sizes, quite cheaply, so that those new quarries, which are from time to time announced, must encounter a slow market at the start, unless they are able to furnish, in all the requisite perfection, the largest sizes used. The qualities of a good stone are homogeneous-ness, with freedom from veins, specks, and flaws, a yellowish white, or a pearly-gray color which is uniform, a hard, fine, uniform grain, a conchoidal fracture with a good degree of strength, and a capacity for receiving good grained or polished surfaces, and of being uniformly acted on by acids. Autographic printing is not now much used, though cases frequently occur in which, it is very convenient or even important. Special attention, in transfer printing, is to be devoted to the quality of the paper used. The paper has a great effect both on the clearness of the printing and the duration of the transfer.— Transfer printing, even as it is now practiced, must be called eminently useful. Senefelder himself used it, though quite imperfectly, of course ; but it is only during the past twenty years that its capacities have been really de- veloped. The rapid improvement it has experienced makes it almost certain, that before many years more it will have become quite perfect and certain in its results. It is now very far advanced in France, the home of lithographic art and science, as the maps of departments, printed by the Government, fully establish. The plates of the great topographical survey of the interior of France are rearranged by transfer, into excellent maps of the departments, with special borders and titles, and full letter press statistical notes, printed from movable type, and transferred into the proper spaces. In England and Scotland, plate-transfer printing is prosecuted as a business, though with what success I have not the means of knowing. In this country, the great amount of transfer from stone on to stone, in making up checks, bills, labels, &c, supplies many shops with petty jobs in one species of transfer; but a few only are engaged in transferring large steel or copper plates. To do this well requirfs a man to make plate-transferring his bushiss, ant1 otherwise, not only will he fail of success, le will be apt to seriously injure or delace piates entrusted to his handling. Our principal establishments in which plate-transfer printing is extensively executed are, J. Ackerman's, No. 379 Broadway, N. Y.; D. McLellans, No. 26 Spring street, N. Y.; Wagner & Mcu>ui-gan's, Franklin-square, Philadelphia ; and Du-val's, Philadelphia. The plates of the Coast Survey Report have been in part printed by each of these establishments, though sometimes their work has furnished very poor evidence of any skill in managing this process. It was by being tor the last two seasons assigned to the charge of inspecting the work on these plates, executed Dy the two first-named establishments, that I was led to such an acquaintance with the subject as to induce me to make this communication. (To be Continued.)