ACOUSTICS APPLIED TO PUBLIC BUILDINGS. 223 



pie, and in some cases with the climate, hut also with the material to 

 be employed in construction. The use of iron and of pjlass requires 

 a modification of style as much as that which sprung from the rocks of 

 Egypt, the masses of marble with which the lintels of the Grecian 

 temjiles were formed, or the introduction of brick by the Romans. 



The great tenacity of iron, and its power of resistance to crushing, 

 should suggest for it, as a building material, a far more slender and 

 apparently lighter arrangement of parts. An entire building of iron, 

 fashioned in imitation of stone, might be erected at small expense of 

 invention on the part of the architect, but would do little credit to his 

 trutlifulness or originality. The same may be said of our modern 

 pasteboard edifices, in which, with their battlements, towers, pinna- 

 cles, "fretted roofs and long drawn aisles," cheap and transient mag- 

 nificence is produced by painted wood or decorated plaster. I must 

 not, however, indulge in remarks of this kind, but must curb my feel- 

 ings on the subject, since I speak from peculiar experience. 



But to return to the subject of acoustics as applied to apartments 

 intended for public speaking. While sound, in connexion with its 

 analogies to light, and in its abstract principles, has been investi- 

 gated within the last fifty years with a rich harvest of results, few 

 attempts have been successfully made to apply these principles to 

 practical purposes. Though we may have a clear conception of the 

 simple operation of a law of nature, yet when the conditions are va- 

 ried, and the actions multiplied, tlie results frequently transcend our 

 powers of logic, and we are obliged to appeal to experiment and ob- 

 servation to assist in deducing new consequences, as well as to verify 

 those which have been arrived at by mathematical deduction. Further- 

 more, though we may know the manner in which a cause acts to pro- 

 duce a given effect, yet in all cases we are obliged to resort t > actual 

 experiment to ascertain the measure of effect under given conditions. 



The science of acoustics as applied to buildings, perhaps more than 

 any other, requires this union of scientific principles with experimen- 

 tal deductions. While, on the one hand, the application of simple 

 deductions from the established principles of acoustics would be un- 

 safe from a want of knowledge of the constants which enter into our 

 formula), on the other hand, empirical data alone are, in this case, 

 entirely at fault, and of this any person may be convinced who will 

 examine the several works written on acoustics by those who are 

 deemed practical men. 



Sound is a motion of matter capable of affecting the ear with a sen- 

 sation peculiar to that organ. It is not in all cases simply a motion 

 of the air, for there are many sounds in which the air is not concerned ; 

 for example, the impulses wliich are conveyed along a rod of wood 

 from a tuning-fork to the teeth. When a sound is produced by a 

 single impulse, or an approximation to a single impulse, it is called a 

 noise; when by a series of impulses, a continued sound, &c. ; if the 

 impulses are equal in duration among themselves, a musical sound. 

 This has been illustrated by a quill striking against the teeth of a 

 wheel in motion. A single impulsel'rom one tooth is a noise, from a 

 series of teeth in succession a continued sound; and if all the teeth 

 are at equal distances, and the velocity of the wheel is uniform, then 



