No. 244-1 193 



modern nation even at this late day, have been able to equal them in 

 this respect, notwithstanding we boast elegance and magnificence. 

 The Chinese have constructed a bridge of a single arch, the materials 

 laid in mortar, the span of which is six hundred feet, and the 

 height of the arch seven hundred and fifty feet. The middle arch of 

 Westminster bridge, London, is only seventy-six feet span, and springs 

 from about two feet above low water mark. The middle arch of Black 

 Friars bridge is one hundred feet span, built in the elliptic form. And 

 the most stupendous bridge in all Europe is that over the Tave, in 

 Glamorganshire, consisting of one arch, the segment of a circle, the 

 diameter of which is one hundred and seventy -five feet; the chord of 

 the segment is one hundred and forty feet; and the height thirty-five 

 feet. You will therefore observe how far superior the Chinese arch is 

 to the best in enlightened Europe, by whom the Chinese are called a 

 benighted people. Our common mortar is composed of lime, sand 

 and water, mixed until most as hard as stone. 



ACOUSTICS. 



By R. L. PELL, Pelham, Ulster Co., N. Y. 



Mr. President: — Acoustics is the science which teaches us the true 

 nature of sound, and it is divided into diacoustics, which explains the 

 properties of sound, and the catacoustics, which treats of sound re- 

 flected. Sound is the information which we first receive of external 

 things by the sense of hearing. The ancients imagined that sounds 

 were beings wafted through the atmosphere and felt by our ears. In 

 the early days of philosophy sound was considered a separate exis- 

 tence wafted through the air to our organ of hearing, aifected in the 

 same manner that our nostrils are affected by the sensation of odours. 

 Zeno says " Hearing is produced by the air which intervenes between 

 the thing sounding and the ear." The air is agitated in a spherical 

 form, and moves otf in waves, and falls on the ear in the same man- 

 ner as the water in a cistern undulates in circles when a stone has 

 been thrown into it. 



There is no doubt but the air is the vehicle of sound, which has 

 been established by the fact, that a bell rung in a .vacuum emitted no 

 sound, when one rung in the air condensed gave aloud sound. Solid 



[Assembly, No. 244.] N 



