No. 244. 1 196 



echo but not the voice; and with surprising variations, sometime 

 soft, sometimes loud, sometimes near, and then distant. There is an 

 echo near the city of Rouen in France, very similar to this. M. 

 Sauvear made some experiments on organ pipes, and found that a 

 body which gives the greatest harmonic sound, and that the shrillest 

 sounding body vibrates 51,100 times in a second. Colladon states 

 that by plunging a thin tin cylinder a few feet under the water, closed 

 at the lower end, and open at the upper end, he was enabled to hear the 

 sound of a bell struck under water at the distance of nine miles. 

 You may take a stick of timber 400 hundred feet long, and place a 

 man at one end with orders to scratch it with a needle, and although 

 ^he sound will not be perceptible to him, the man|at the other end 

 will hear it most distinctly. Parry's account of his third expedition 

 to the north polo states, that two persons could converse with each 

 other across Port Bowen harbor, a distance of one mile and a quarter. 

 Derham relates with regard to distances, that guns fired at Cailseroom 

 were heard across the south extremity of Sweden as far as Denmark, 

 a distance of nearly 119 miles. Doct. Kearn, a Swedish physician 

 mentions that he heard guns fired at Stockholm, a distance of 180 

 miles. The firing of cannon in a fight at sea between the Dutch and 

 the English in 1672, was heard at Shrewsbury in England, 200^miles 

 distant from the scene of battle. 



