Herrn Geheimen Rath Bessel. Von C. Rümker. Hamburg,

1847. 4to.-From Professor Rümker.

Agricultural Botany: An Enumeration and Description of Useful Plants and Weeds, which merit the notice or require the attention of American Agriculturists. By William Darlington, M. D. Philadelphia, 1847. 12mo.-From the Author.

A Brief Notice of the Life, Researches and Discoveries of Friedrick Wilhelm Bessel. By Sir J. F. W. Herschel.

ADDITIONS TO THE LIBRARY BY PURCHASE.

Scientific Memoirs. Edited by Richard Taylor, F. S. A. Vol. V. Part XVII. May, 1847. 8vo.

The London, Edinburgh, and Dublin Philosophical Magazine.

Vol.

XXX. Nos. 203, 204 and 205. June and July, 1847. 8vo. Astronomische Nachrichten. Nos. 597 to 603, inclusive. 4to. The Edinburgh New Philosophical Journal. Conducted by Professor Jameson. No. 85. April to July, 1847. 8vo.

A communication from Mr. Richard A. Tilghman, on the Decomposing Power of Water at high temperatures, was read and referred to a Committee, consisting of Prof. Frazer, Dr. Bache and Dr. Patterson.

A communication was read from Professor Rümker, containing his latest observations on the planet Astræa, and also his observations on the Comet lately seen.

My dear Sir, I take the liberty of sending you herewith the second part of my treatise on occultations of fixed stars, with a few copies for distribution.

I take the opportunity of communicating to you my latest observations of the planet Astræa.

I join here my observations of the Comet lately seen.

Mr. Niebour, assistant at the Hamburg Observatory, has thence computed:

Perihelion passage, June 184.08925 mean Greenwich time.

Mr. M'Culloh made some observations on the application of polarized light to chemical analysis.

After alluding briefly to the discovery of the property of circular polarization in quartz, by M. Arago, and to the subsequent investigation, by M. Biot, of the laws of that phenomenon, as exhibited by certain liquids as well as by quartz, Mr. M'Culloh remarked, that but few analytical chemists seem to have availed themselves of the advantages which circular polarization presents for the extension of chemical knowledge. They appear to have considered its application to practical purposes beset with laborious algebraic calculations, and troublesome manipulations. And some who have only made a few imperfect analysis by this optical method of M. Biot, have even ventured to assert that simpler and quicker methods of attaining the same results are very desirable; while others have doubted the exactness of optical analysis, rather from want of sufficient evidence or information on the subject, than from any positive reason for disbelief.

His attention had been particularly devoted to this subject, in consequence of a very extensive series of chemical researches in relation to the manufacture of sugar, and the chemical nature of the cane and its various products; which researches were made by him under the superintendence of Prof. A. D. Bache, and the direction of the Secretary of the Treasury, in obedience to an act of Congress. In the performance of these researches, he had also been assisted by Mr. Reynolds, an able young chemist of this city. They were designed to obtain information for the use of the government, and indirectly to promote the sugar industry of our country. Several hundred saccharine substances were carefully analyzed; and the processes of manufacture and refining in Cuba and the United States were fully examined. The practical results thus obtained, constitute the subject of a report made to the Secretary of the Treasury, and by him communicated to the Senate at the close of the last session of Congress.

Incidentally, these investigations had served to throw light upon matters of a purely scientific nature; which had, therefore, been omitted, as inappropriate in the report to Congress; but which, for that very reason, were proper subjects for the attention of this Society.

He had referred to his labours thus particularly, that he might justify himself in presuming to pronounce incorrect the opinions of chemists of acknowledged reputation and skill. And he thought

VOL. IV.-3 A

that, after having been constantly occupied, for nearly two years, in making chemical investigations by means of polarized light, he might venture to speak with some confidence upon these matters, without being guilty of immodesty.

With reference to the objection, that the mathematical calculations are troublesome, he observed, that they are perfectly simple, and may be performed by mere arithmetical multiplication, division, &c.; that logarithms facilitate them; and that, by varying only the substance, all other circumstances being constant, the calculations of a series of optical results become as short and as easy as those of quantitative analysis made by the ordinary dry and humid methods with the common balance.

As the result of the experience of Mr. Reynolds and himself, after many hundred analyses, he stated, that five or six independent and complete analyses may be made in a day by a single person, and that by introducing method into all the manipulations, even a larger number may readily be performed. He, therefore, believed that no objection of time can be urged against such analyses; nor would any one familiar with the manipulations of modern analytical chemistry find just cause to complain of those of optical examinations after a few days practice.

Of the accuracy of quantitative determinations by circular polarization, he observed that the theory of the method is based upon rigid mathematical deduction, and is, therefore, perfectly exact; all possible errors are consequently those of observations only. The mean error of reading an angle of rotation, with the apparatus he had employed, does not exceed one-tenth of a degree, which for solutions of sugar corresponds to 0.002, or two-tenths of a per cent. The most exact assays of gold or of silver, by the humid method of Gay Lussac, made by experienced assayers at the mint of the United States, with balances far more delicate than those employed by analytical chemists, are affected with a probable error of 0.0002, plus or minus. Hence optical determinations compare advantageously with the results of ordinary analysis. That such determinations are fully entitled to confidence, is also proved by checking them with other methods, and especially that of applying them to known synthetical mixtures.

In conclusion, Mr. M'Culloh remarked, that he had for some time been prevented, by official and other duties, from completing a series of experimental researches with reference to the effects of temperature upon the phenomena of circular polarization, and also concerning the

nature of the union, whether chemical or mechanical, which takes place when solid substances are dissolved in water, alcohol and other liquids. He hoped, however, to be able to present these investigations in a definite form to the Society before long. And he considered the subject one full of interest and importance, by reason of its intimate connexion with the molecular forces and constitution of matter, and its relation to certain recently discovered electro-dynamical phenomena.

On motion of Dr. Patterson, the Proceedings of the Society for the present year were directed to be sent to the publisher of the Literary World, New York.

Pending nomination, No. 197, and new nominations, Nos. 198-201, were read.

Stated Meeting, September 17.

Present, twenty-three members.

Dr. CHAPMAN, President, in the Chair.

Mr. Townsend, a member of a corresponding society, was introduced.

A letter was received and read:

From the Royal Bavarian Academy of Sciences, dated Munich, 24th of April, 1847, acknowledging the receipt of Transactions and Proceedings of this Society, and of Dr. Dunglison's Public Discourse on Mr. Du Ponceau.

The following donations were announced:

FOR THE LIBRARY.

Report of the Sixteenth Meeting of the British Association for the Advancement of Science; held at Southampton, in September, 1846. London, 1847. 8vo.-From the British Association. Abhandlungen der Mathematisch-Physikalischen Classe der Kœniglich Bayerischen Akademie der Wissenschaften. Vierter Band die Abhandlungen von den Jahren 1844-46, enthaltend. München, 1846. 4to.-From the Royal Academy of Munich.