214 
UR. SIMONS ON THE VELOCITY OF SOUND. 
with the result of experiment. Employing MM. Gay-Lussac’s and Welter’s 
co-efficient, the differences between the observed and calculated velocity are 
constantly affected with the same sign ; whereas in taking K from M. Dulong, 
the differences are sometimes positive and sometimes negative. It is therefore 
presumed that M. Dulong’s labours bring the calculation of the velocity of 
sound much nearer to the truth than before, and that such differences as are 
yet remaining between calculation and experiment, may be attributed, with 
great probability, to errors unavoidable in such complicated observations. 
Utrecht, December 30, 1829. 
