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* MENDELEEFF. 309 MENDELSSOHN-BABTHOLDY. he published his Organic Chemistry. He was iiiiule professor of flieniistry at the Saint Peters- burg Institute of Technology in 1803. anil three years later at the university, la 1871-73 he made extensive studies on the compression of gases, embodied in his On the Elasticity of Uuscs. la 1870 he «'as conunissioned by the authorities to study the petroleum industry in Pennsylvania and the Caucasus. His work on Aqueous Solu- tions (1880) was received by chemists as a notable contribution to experimental chemistry, althou^'h Ills 'theory of .solutions.' according to which stilvents invariably form definite or 'in- definite' dicmical compounds with the substances dissolved in them, has been strongly criticised by physical chemists of the miMlern tJerman schools. As member of the Council of Commerce and In- dustries, MendelOelT became the champion of pro- tection of home industries, and the policy of Russia in that direction dates practically from the jJublication of his Tariff Elucidated (1890). He worked out the formula for the pyroeoUodial smokeless powder, serviceable for all firearms, when Russia undertook to rearm her forces. In 1893 he was made conservator of weights and measures in the new Chamber of Weights and Measures established in the Department of Finance. His Elements of Chemistry (1808-70, 5th ed., Saint Petersburg, 1889) is a standard work and has been translated into English, CJernian, and French. In it he first set forth the theory later embodied in La loi periodique des elements chi- miqttes (Paris, 1879), now known as the periodic law (q.v. ), in the following formula; "The properties of the elements, as well as the forms and ]n'operties of their compounds, are in periodic dependence on. or form a periodic function of, the atomic weights of the elements." This law en- abled Mendeleett' to foretell the existence and even the jiroperties of several unknown elements, whidi have since lieen actually discovered. Mcndeleeff's scientific contriliutions. dealing mostly with physical chemistry, and numbering upward of 150, have appeared in several (icnnan and French scientific periodicals. Consult T. E. Thorpe, Essays in Historical Chemistry (London, 1894). MENDEL'S LA"W. See HYBRiniTT. MENDELSSOHN, men'dcl-son, ilosEs (1729- 86), A (ierman ]jhiloso])her of Jewish pai'entage. He was born September 0, 17"29, at Dessau. From his father, a schoolmaster and scribe, he received his first education; and in his thirteenth 3'ear procceiled to Berlin, where, amid very indigent circumstances, he contrived to learn Latin and modern languages, and to apply himself to the study of philosophy. After many years of com- parative poverty he became part heir to a rich silk manufacturer, whose children he had educated. The intimate friend of men like Les- sing — whose yathan der ^Veise had its jirototype in him — Sulzer, and Nicolai, he contributed in a vast degree to the mitigation of the brutal preju- dices against the .Jews. On the other hand, he broadeneil the outlook of his own co-religionists. He died .lanuary 4, 1786. His principal works are : Pope, fill Mrtdjihysiker (with Lessing) (1755); Briefe iiber die Empfindunqen (1755) ; TJeber die Eridenz in den metaphysischen Wissenschaften : Pluidnn, oder Uber die Unsterblichkeit der Keele (I7fi7): Jerusalem, oder iiber reliyidse Maeht iind -/udenthum (1783); and Morgenstunden ( 1785), His works have Ijeen collected and edited by 6. B. Mendelssohn (7 vols., Leipzig, 1S43- 45). Consult: llensel. Die Eamilie Mendelssohn (9th ed., Berlin, 1898; Eng. trans. London, 1882); Kayscrling. Moses Mcndelssuhn (Leipzig, 1882) ; Ritter, Mendelssohn und Lessing (Ber- lin, 188C) ; Dessauer, Der dcutsche Plato (ib., 1879), His philosophy was of a rather super- ficial popular sort, whose aim was to find good reason for opinions currently regarde<l as cor- rect. MENDELSSOHN - BARTHOLDY, men'del- son-blir-tol'di, Fklix (lH9-47). A famous Ger- man composer. He was born at Hamburg, Febru- ary 3. 1809. the son of Abraham ilendclssohn and Leah Salomon. The hitter's brother, after embrac- ing Christianity. as.sumed the name Bartholdj', which the Mendelssohns then added to their fam- ily name. The family was wealthy and highly refined. Felix's grandfather was the celebrated Moses Mendelssohn (q.v.). His children were brought up in the Protestant faith. Felix re- ceived piano instruction first from his mother; afterwards Ludwig Berger became his teacher. His instructor in counterjioint and musical com- position was Zelter: and the finishing touches to his skill as a pianist were given by Moscheles. His eldest sister, Fanny, shared this instruction. Mendelssohn began to compose before he was twelve years of age, and also showed great taste in drawing, and was rapid, yet accurate, in his general studies. Notwithstanding his remark- able achievements for one so young, his education continued on broad lines, jluch of the charm which he exerted through life was due to his combining with musical genius the tastes of a man of high culture. Vhen eleven years old he paid a visit to Goethe, who was delighted not only with his musical accomplishments, but with his modesty and refinement. The home of the ilendclssohns was the centre of a cultured circle. At the Sunday concerts which were given there the most eminent people residing or visiting in Berlin were met — musi- cians like Weber, Spohr. Paganini, Liszt, Schu- mann; painters like Ingres, Vernet. Verboeck- hoyen, Kaulbach ; singers like Lablaehe, Grisi, Pasta; and in addition to these, actors, sculptors, poets, and scientists, among the latter the Hum- boldts, Bunsen, and Jakob (Jrimm. One can imagine the rich life which unfolded itself within such a circle, and its iiufluence upon Felix's development. One of the intimates of the circle was Hensel. the portrait painter, who married Fanny, herself scarcely inferior to Felix at the piano. Notwithstanding his pronounced musical gifts, Feli.K's father, in order to make sure that he was acting wisely in the choice of a musical career, took him in 1825 to Cherubini in Paris. After examining several of the boy's composi- tions, Cherubini gave an allirmative answer. In the same year Mendelssohn composed his o<'tet (Opus 20). In February, 1827. Iiis Midsummer Kifiht's Dream overture was ]ilaycd at Stettin, and was received with great applause. April of the same year saw the production of his opera. The Wedding of Camacho, in Berlin, but it was not a success. In 1828 he composed his overture to Goethe's poem, A Calm Sea and a Happy Voyage; and a letter from Fanny. December 8, 1828, to his friend, the poet Klingemann, refers to his com- position of Songs Without Words. One of Men-