CONDUCTOR. 263 CONE. operatic performances were conducted from the liarpsicliord. In the recitative, the leader struck the few chords upon the instrument, and in the concerted pieces he led. This he did by mxlding the liead, stamping the foot, and using one arm or even both arms. When the opera reached France and Germany, this mode of conducting was naturally employed in these countries also. In Italy this method maintained itself up to the iirst half of the nineteenth centuiy. In Ger- many we find before 1700 that at performances of sacred works in churches the organist was assisted by a time-beater. This time-beater was not a conductor: he only indicated the time. But shortly after the beginning of the eighteenth cen- tury the Italian operatic method was adopted for the church, and the org-anist was the sole director, as is still the custom in churches of to-day. The earlier sjinphonic works were also conducted from the harpsichord. When the number of Avind instruments increased, it was found that the tones of the harpsichord could not be heard by all players, and the time-beater again made his appearance. In this manner Haydn and ilozart conducted their symphonies, they sitting at the harpsichord while some one else beat time. Beethoven conducted with the baton, and the first violin or concert-master assisted. Interpretative conducting may be said to have begun with Stamitz (1719-01) and his pupil Cannabich (1731-98), whom Mozart called the best conductor he ever heard. Cannabich devel- oped the crescetjdo and diminuendo of the orches- tra, one of the great means of expression. Gossec (1738-1829) must also be mentioned among the early conductors who developed orchestral tech- nics. But these men were exceptions at their time. Inter])retative conductors as a class did not e.xist before the beginning of the nineteenth century. Among these the greatest were Spohr, ^^'eber, and Jlendelssohn in Germany, and Habe- neck, a German by birth and training, in France. With. Wagner and Berlioz begins the school of modern conducting, which is the culmination and natural development of the work begun by the four eminent conductors just mentioned. Nearly all the gi-eat modern conductors are German. France boasts three great names — Pasdeloup, Co- lonne, and Lamoureux. But among the Germans there are Liszt, Biilow, Richter, Seidl, IMottl, R. Strauss, Weingartner, Nikisch, Paur, Lohse, Levi, Zumpe, Sucher, Tliomas. Among the best trea- tises on conducting are: Wagner, Vcher das Diri- yicren (vol. viii. of his collected works, Leipzig, 1888) ; Berlioz, Treatise on Modern Instrumenta- tion, translated by Bennett (London, 1882) ; Hen- derson, The Orclicstra and Orchestral Music (New York, 1809). CONDUCTOR and INSULATOR OF ELECTRICITY. The property of electrical conductivity is possessed in some degree by all known substances. There is, hoAvever, an enor- mous difference between the conductivity of those that are used as conductors and those that are used as insulators, the former having many million times the conductivity of the latter. The substances at the lower end of the scale are therefore of sufficiently low conductivity to serve for covering and supporting wires made of the good conductors, without permitting any serious escape of an electric current when the wires are charged. In transmitting electricity from point to point, through telegraph or tlectrie-light lines, for ex- ample, those substances possessing the greatest conductivity, such as copper and iron, are selected to form a path for the current, and these are sur- rounded with materials whidi have the least con- ductivit.y or od'er the highest resistance, such as air, rubber, and glass, in order to confine the current and compel it to travel to the end of the line. When a conductor is so surrounded or so placed on non-conducting supports that it pre- vents the electricity communicated to it from passing into the ground or escaping, it is said to be insulated. As the difference between conductors and in- sulators is merely one of degree, there is, even under the best conditions, a loss in the transmis- sion of electricity over a line of wire proportion- ate to the amount of leakage through the insula- tion and the resistance to travel oll'ered by the wire itself, since the slight eH'ort required of the current to force its way ahead through the wire causes some of it to escape through the insula- tion in the same way that water forced through a long pipe will escape in small quantities at weak points. It is, indeed, extremely necessary to prevent conductors buried in the earth from having any connection with water or dampness, and. if the insulation of the conductor is defective in a damp spot, a certain jiroportion of the cur- rent will leave the conductor and travel through the earth. Chemically pure water is a non-con- ductor, but as found in the earth, water is an excellent conductor on account of the materials it holds in solution. The electrical conductivity, and its reverse, the resistance of materials, are, therefore, subjects of great importance to electricians; and the selec- tion of materials of high conductivity or low re- sistance for wires, and materials of high resist- ance for insulators, receives careful attention. The best conductors are gold, copper, silver, alumi- num, brass, iron, and all other metals. The best insulators, or the worst conductors, are dry air, glass, mica, porcelain, paraffin, rubber, silk, gutta-percha, and almost aU the hydrocarbons. The intermediate substances are many liquids and damp substances, carbons, minerals, and com- pound substances. The couductivity of all sub- stances is greatly affected by changes of tempera- ture. An increase of temperature increases the resistance of all the metals, while it has the opposite effect in other substances. Glass loses its insulating properties at a red heat, and so do wax, sulphur, amber, and shellac when fused. Glass, if not the most perfect insulator, far ex- ceeds others in hardness and duraliility. and is much employed as insulation for light electrical apparatus. Hard rubber or vulcanite enters into the construction of much electrical apparatus on account of its high resistance. Paraffined paper is also employed for condensers (q.v.), while for the armatures of djmamos and motors mica is used. See Electkicitt. CONE (Lat. contis, Gk. kuvo^, honos, cone, Skt. suna, whetstone, from id, to sharpen). A solid formed by a plane cutting all of the ele- ments of a conical surface. A conical surface is generated by a line called the generatrix pass- ing through a fixed ]ioint and tracing a fixed curA-e called the directrix. If the line is unlim- ited it generates two conical surfaces, on opposite sides of the point (vertex), called the nappes of
