514 LECTURE LIII. 



will take its course, in preference to a given length of air, or of any other 

 standard of comparison. The substances, which conduct electricity the 

 most readily, are metals, well burnt charcoal, animal bodies, acids, saline 

 liquors, water, and very rare air. The principal nonconductors are glass, 

 ice, gems, dry salts, sulfur, amber, resins, silk, dry wood, oils, dry air of 

 the usual density, and the barometrical vacuum. Heat commonly increases 

 the conducting powers of bodies ; a jar of glass may be discharged by a 

 moderate heat, and liquid resins are capable of transmitting shocks, 

 although they are by no means good conductors : it is remarkable also that 

 a jar may be discharged by minute agitation, when it is caused to ring by 

 the friction of the finger. It has been observed that, in a great variety of 

 cases, those substances, which are the best conductors of heat, afford also 

 the readiest passage to electricity; thus, copper conducts heat more 

 rapidly, and electricity more readily, than iron, and platina less than 

 almost any other metal ; glass also presents a considerable resistance to the 

 transmission of both these influences. The analogy is, however, in many 

 respects imperfect, and it affords us but little light, with regard either to 

 the nature of heat, or to that of the electric fluid. 



LECT. LIII. ADDITIONAL AUTHORITIES. 



Treatises on Electricity. Mortensson, De Electr. 4to, Upsal, 1740. Desa- 

 guliers, A Dissertation concerning Electr. 1742. Winckler's Gedanke von der 

 Elektr. Leipz. 1744. Eigenschaften der Elektr. Materie, 1745. Bose, Recherches 

 sur la Cause de 1'Electr. 4to, Berlin, 1745. Tentamina Electr. 4to, Wittemb. 1747. 

 Waitz, Abhand. von der Elektr. 4to, Berlin, 1745. Piderit, De Electr. Marb. 1745. 

 Watson's Exp. and Obs. with Sequel, 1746. Miiller, Ursachund Nutzen der Elektr. 

 1746. Nollet, Essai sur 1'Electr. 12mo, Paris, 1746. Recherches sur do. 4to, 

 1749. Lettres sur do. 12mo, 1753. Martin on Electr. Bath, 1748. Jallabert sur 

 1'Electr. 1749. Boulanger, Traite de I 7 Electr. 12mo, 1750. Secondat, Obser- 

 vations Physiques, 12mo, 1750. Verrati sur 1'Electr. 12mo, Montp. 1750. 

 Buia, Electr. Effectuum Explicatio, 1751. Franklin, Exp. and Obs. 4to, 1751- 

 54. Navarro, Physica Electr. Madrid, 1752. Klingenstierna, Electr. Stockholm, 

 1755. Beccaria, Lettere dell' Elettr. fol. Bolog. 1758 (tr.), Lond. 1776; Ex- 

 perimenta, 4to, Turin, 1772. Egelin, De Electr. 4to, Utrecht, 1759. Wesley's 

 Electr. made plain, 12mo, 1760. Saussure, De Electr. Geneve, 1766. Lullin, 

 De Electr. Geneve, 1766. Hartmann's Versuche in leeren Ratime, Hanov. 

 1766. Priestley's Introduction to Electr. 1769. Ferguson's Introduction to 

 Electr. 1771. Sigaud de la Fond, Traite de 1'Electr. 12mo, 1771. Precis des 

 Phenomenes Electr. 1781. Jacquet, Precis de 1'Electr. Vienna, 1775. Gross, 

 Elektrische Pauschen, Leipz. 1776. Dubois, Lettres sur 1'Electr. 1776. Bar- 

 letti (R. S.) 1771. Socin, Anfangsgriinde der Elektr. Hanau, 1777. Gallitzin 

 sur 1'Electr. 4to, Petersb. 1778. Lord Mahon's Principles of Electr. 4to, 1779. 

 Wilson's Short View of Electr. 4to, 1780. Lyons's New System of Electr. 4to, 



1780. Marat, Recherches sur 1'Electr. 1782. Lacepede sur 1'Electr. 2 vols. 



1781. Cuthbertson, Van der Elektr. Amst. 1782-94. D'Inarre, Naturlehre, 

 Frankf. 1783. Adams, Essay on Electr. 1784. Donndorff's Lehre von der Elektr. 

 Erf. 1784. Tressan sur la Fluide Electr. 2 vols. 1786. Priestley's Introd. to 

 Electr. 1787. Beck, Lehre von Electr. 1787. Langenbucher's Elektr. Augs. 1788. 

 Bennet's Experiments, Derby, 1789. Briefe iiber die Elektr. von C. L. Leipz. 1789. 

 Brook on Electr. 1790. Peart on do. Gainsborough, 1791. Lampadius, Ueber 

 Electr. und Warme, Berlin, 1793. Cavallo's Electr. 3 vols. 1795. Morgan's 

 Lectures on Electr. 2 vols. 12mo. Saxtorph, Darstellung der Elektr. 2 vols. 

 Copenh. 1803. Deluc, Traite Elementaire sur le Fluide Electro-galvanique, Milan, 

 1804. Sammlung Elektr. Spielwerke, Niirnb. 1804. Robison's Mechanical Phi- 

 losophy. Singer's Elements of Electr. 1814. Galle, Beitrage zur Erweiterung der 

 Elektr. 2 vols. Salzb. 1816. Adams's Electricity, 4to, 1823. Roslin, Priifungvler 



