To complete our knowledge of the transmission of sound through gases, a table is here added from the excellent researches of Dulong, who employed in his experiments a method which shall be subsequently explained: VELOCITY OF SOUND IN GASES AT THE TEMPERATURE OF 0° C. Velocity Air 1,092 feet Oxygen 1,040 ” Hydrogen 4,164 ” Carbonic acid 858 ” Carbonic oxide 1,107 ” Protoxide of nitrogen 859 ” Olefiant gas 1,030 ” According to theory, the velocities of sound in oxygen and hydrogen are inversely proportional to the square roots of the densities of the two gases. We here find this theoretic deduction verified by experiment. Oxygen being sixteen times heavier than hydrogen, the velocity of sound in the latter gas ought, according to the above law, to be four times its velocity in the former; hence, the velocity in oxygen being 1,040, in hydrogen calculation would make it 4,160. Experiment, we see, makes it 4,164. The velocity of sound in liquids may be determined theoretically, as Newton determined its velocity in air; for the density of a liquid is easily determined, and its elasticity can be measured by subjecting it to compression. In the case of water, the calculated and the observed velocities agree so closely as to prove that the changes of temperature produced by a sound-wave in water have no sensible influence upon the velocity. In a series of memorable experiments in the Lake of Geneva, MM. Colladon and Sturm determined the velocity of sound through water, and made it 4,708 feet a second. By a mode of experiment which you will subsequently be able to comprehend, the late M. Wertheim determined the velocity through various liquids, and in the following table I have collected his results: TRANSMISSION OF SOUND THROUGH LIQUIDS Name of Liquid Temperature Velocity River-water (Seine) 15° C. 4,714 feet ” ” 30 5,013 ” ” ” 60 5,657 ” Sea-water (artificial) 20 4,768 ” Solution of common salt 18 5,132 ” Solution of sulphate of soda 20 5,194 ” Solution of carbonate of soda 22 5,230 ” Solution of nitrate of soda 21 5,477 ” Solution of chloride of calcium 23 6,493 ” Common alcohol 20 4,218 ” Absolute alcohol 23 3,804 ” Spirits of turpentine 24 3,976 ” Sulphuric ether 0 3,801 ”