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COHEN. 123 COHOES. into closer connection with the sciences. His contributions to the interpretation of Kant's writings are of iJermanent value. His works include Kant's Tlicorii; dcr Erfahrunq (2il ed. (1895) ; Kant's licrjrunduntj dcr Ethik (1877) ; Platan's Idcenlchrc untl die MuthciniiliL- { 18711) : Ein Bekenniniss und die Judiiifruge (1880) ; Die Nachstenliebe im Talmud (1884); Kant's Be- griindung dcr Aesthetik (1889). COHERER (from cohere, from Lat. cohw- rcrc, to cling together, from co-, together + hwrere, to cling). An instrument invented in 1890 by Professor Branly, of Paris, for the de- tection of so-called 'electrical waves,' that is, of waves in the ether produced by electrical oscillations. (The principle of this action had been discovered before by Varley and Calzecchi- Onesti.) It consists essentially of a tube con- taining minute filings of some metal, into each end of which a wire enters for a sufficient dis- tance. It has been observed that under ordi- nary conditions such a tube does not allow an electric current to pass; but, if electrical waves fall upon it, a current can be passed most easily, thus affording a simple means of telling when electrical waves are passing. One explanation is that, when put in the tube loosely, the filings do not make electrical connection, owing to thin surface layers of condensed gases, etc. ; but under the action of the electrical waves these layers are cleaned off, possibly by minvite sparks passing between the filings, and thus establish- ing metallic connection through the tube. If, after the waves have passed, the tube is tapped forcibly, the filings are knocked apart, and the tube again liecomes a non-conductor. The metals whose filings are used ordinarily are silver and nickel. Others might be used, but it has been shown that with some substances the electrical resistance is increased by the waves, not de- creased. Sec Wireless Telegr.phy. COHESION (Fr. cohesion, It. coesione, from Lat. eohccrcre, to cling together). The name given to that property of matter observed when two portions of the same matter are brought closely into contact ; thus one speaks of the cohesion of water, meaning the forces manifest at any point in water owing to the mutual ac- tion of the molecules. Sometimes the word is used to express the phenomenon observed when two pieces of a solid are stuck together, such as two pieces of glass, two pieces of lead, etc. The forces of cohesion in a liquid are greatly affected by having substances dissolved in it, and, in short, by anything which affects the molecules or their arrangements. COHN, kon, Ferdin-akd Julius (1828-98). A Gennan botanist, born at Breslau. He studied at the universities of Berlin and Breslau, be- came connected with the latter institution in 18.50, and was made full professor there in 1872. His investigations concerned chiefly the physi- ology and morphology of plants, to our knowl- edge of which he made numerous contributions of the highest importance. Besides a number of papers on special topics of his science, his pub- lished works include the following: Zur Naturge- schichte des Protococcus pluviaiis (1850); Vn- tersuchungen iibcr die Entimckehingsgeschichte der mikroskopischen Algen und Pilze (1853); Neiie Vntersuchungen iiber Bakterien (1872-75) ; Die Pflanze, Vortriige aus dem Oebiete der Bo- Vol. v.— 9. tunik (2d ed., 1895-97). He also edited the Beitrayc ::iir Biologie der Pflan^eii and the Kryp- toganicn/lura Hchleiiicns. One of his best-known contributions to science was the demonstration that bacteria are vegetal organisms. Consult Pauline Cohn, Fcrdimind Cohn, BUitter der Erin- ncrung (Breslau, 1901). COHN, GusT.vv (1840—). A German politi- cal economist. He was born at llarienwcrdcr, and studied at Berlin and .Jena. His tour through England in 1873 gave him the maleriaU for his work, Vntcrsuehunyen iiber die cnglisclte Eisenbahnpoliiik (1874). In 1884 he became pro- fessor of political science at Gottingen, and in 1892 served as a member of the Imperial Com- mission ajjpointed to investigate the affairs and regulations of the Stock Exchange. His more im- portant works include: System der KatiotHiliJkoii- omie (1885 and 1889; Engl, trans, in the Econo- mic Studies of Chicago University) and Zur (leschiehtc und Politik des Verkehrswesens (1900). COHNHEIM, kOn'hIm, .Julius Friedrich (1839-84). A German pathologist, boni at Demmin in Pomerania. After studying medi- cine at several universities, including those of Berlin and Wiirzburg, he became connected with the pathological institute of the Charite, Berlin. In 1808 he was made professor of pathology at Kiel, ■ from 1872 to 1878 was professor at Breslau, and during the last years of his life held a similar position at Leipzig. His pub- lished works include the following: Unter- suchungen iiber die embolischen Prozesse ( 1872) ; Neue Untersuchungen iiber die Entziindung (1873) : Vorlesungen iiber allgemeine Pathologie (1877-80); Die Tuherkulose vom Standpunkte dcr Infektionslchre (1881). Cohnheim was the first to demonstrate that pus consists largely of white blood-corpuscles, thus throwing much light on the nature of inflammations. Consult: Ponfick, Gedtichtnisrede auf Cohnheim (Breslau, 1884); also, Kiihne's biographical sketch published with the Gesammelte Abhandlungen von J. F. Cohn- heim (Breslau, 1885). CO'HO (American Indian). A local name in Alaska for the silver salmon (Oneorhynchus ki- siitch) . See S.lmon. COHOES, ko-hoz'. A city in Albany County, X. Y., nine miles north of Albany; at the junc- tion of the Jlohawk and Hudson rivers, and on the Delaware and Hudson .ind the New York Central and Hudson River railroads (Jlap: New Y'ork, G 3). The Erie and Champlain canals also pass through the city, uniting a short dis- tance to the south. In this section of the Erie Canal there are several locks which lift the boats from the lower level of the Hudson Valley to that above the Jlohawk Falls. The city is furnished with abundant water-])ower by the jMohawk, here crossed by a long railroad bridge affording a fine view of the falls, which are 75 feet high and 900 feet wide. A dam above the falls stores the water which is supplied by canals to the mills and factories. Cohoes is noted as a manufacturing centre, its industries including large cotton-mills, Avoolen-mills, knit- ting-mills, axe-factories, rolling-mills, and many other industrial establishments. Cohoes was for n.any years a part of the Rensselaer JIanor. Its first settlers were Dutch, and probably came as early as 1630. It was incorporated as a