NATURAL PHILOSOPHY. 147 



Propagation of Sound in the Air. Newton was the first to study the 

 propagation of motion in the atmosphere, and the solution which he 

 gave still excites the admiration of geometers, and is termed by Laplace 

 " a monument of his genius." Sometimes, however, it does not entirely 

 agree with experience ; for instance, it gives for the swiftness of propa- 

 gation a value of about a sixth below that given by observation. Since 

 his time Lagrange, Euler, Laplace, Poisson, and other geometers, have 

 occupied themselves with this problem with the view of either estab- 

 lishing the true mathematical theory, or discovering the cause of the 

 difference between calculation and experience. The subject has also 

 been taken up by the eminent mathematician Duhamel, who has laid 

 a memoir before his associates of the French Academy, giving his cal- 

 culations, whereby he arrives at this singular consequence, "that the 

 theoretic swiftness of sound in the air, supposing that there is no eleva- 

 tion of temperature, is identical with that given by experience." The 

 hypothesis of an elevation of temperature, which appears so probable, 

 and which comes so conveniently to the assistance of the theory, be- 

 comes a difficulty, and we find ourselves compelled either to demon- 

 strate that this hypothesis is not legitimate, or to find a new and hith- 

 erto unknown cause which shall neutralize the effect. 



Transmission of Sound to a great Distance. Dr. F. C. Robinson, 

 of Greensburg, Westmoreland County, Pa., says that the report of ar- 

 tillery at the battle of Gettysburg, on the 3d of July, was distinctly 

 heard at Greensburgh, a distance of one hundred and twenty-five miles 

 from the seat of conflict ; on lying down on the ground, jarring could be 

 distinctly felt. Dr Robinson says, " That the whole neighborhood 

 claim to have heard the firing. During Friday, the air was~cahn and 

 the sky cloudless." 



Function of the Ear. Prof. Helniholz regards the snail-shell, or 

 cochlea, as the special organ for transmitting musical sounds to the 

 nerves, while noises affect other portions of the ear. The so-called 

 "fibres of Corti," of which there are about three thousand, he considers 

 each capable of being affected by a simple sound, while a compound 

 sound acts upon several, and produces a corresponding impression on 

 the nerves. Each filament of the acoustic nerve is united to an elastic 

 filament, which he supposes to be thrown into vibration by appropriate 

 sounds. 



VIBRATING WATERFALLS. 



The American Journal of Science and Arts, for November, 1863, con- 

 tains an article, by Prof. E. Loomis, discussing anew the subject " vibrat- 

 ing waterfalls" and detailing observations on three vibrating water- 

 falls, namely, in South Natick, Holyoke, and Lawrence, Mass. In 1843, 

 Professor Loomis published an article on this same subject, in which he 

 suggested that the dam itself was the vibrating body, and that the vi-. 

 brations were analogous to those of a stretched cord. Prof. Snell, of 

 Amherst, however, differed from such a conclusion, and in turn attribut- 

 ed the cause of the vibrations to a column of air behind the sheet of 

 water falling from the dam. Prof. Loomis, after an extended series of 

 observations, has apparently abandoned his original views, and arrived 

 at conclusions similar to those of Prof. Snell. A series of careful obser- 

 vations were made, in 1862, by Mr. William Edwards, at the request of 



