PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 639 



This possible attenuation of air will not excite surprise wlicn we con- 

 sider that a grain of gold may be so expanded as to be divided into 4,900 

 millions of i)arts, perceptible with the microscope; but astonishment can- 

 not be repressed upon calculating' the velocity of sound in a fluid vastly 

 less dense than air thus expanded, provided its elasticity remains the same 

 as at tlie earth's surface under the standard pressure and temperature. If 

 we take the comparative rarefaction of such a fluid at only 1,098,304 

 millions, we find its square root to be 1,048,000, \^hich multiplied by 12,38G, 

 the number of miles per minute at which sound moves through air, gives 

 12,980,528 miles per minute as its velocity through such a medium; while 

 the propagation of light through aith is only at the rate of 11,520,000 miles 

 per minute. 



Assuming that any energy generating wave motions in a fluid, in con- 

 sequence of its elasticity, follows the same law, we now have the means 

 of making a comparative estimate of the density of the psth directly envel- 

 oping our globe; and it may be stated in gen lal terms that such asth does 

 not exceed the density which a cubic inch of air would have were it 

 expanded to 1,098,304,000,000 of cubic inches. 



Sound would be propagated, with exactly the velocity of light through 

 a fluid, under the standard pressure, 814,094,104,900 times rarer thalTaiF. 

 Therefore, if the density of air be 1, the density of eeth is represented by 

 the decimal. 000000000000114. 



It will not be inferred from this view that the aim has been to roach 



" The fir t of things, quintessence pure," 



for the elastic quality of eeth involves the hypothesis of a still more subtle 

 fluid. We have raised one curtain only to find another to be raised. As 

 the unfathomed vaults of Heaven recede before the sweep of a more power- 

 ful refractor, and nebulai resolved reveal nebulae beyond, so the most diminu- 

 tive germ that springs from the Creator's touch, discloses through the lens 

 of higher power, new signs of more wonderful mechanism within. Each 

 nucleus has its nuclei! Each entoblast is but the boundary of a micro- 

 cosm! Each particle, a galaxy of atoms revolving in the all-pervading 

 asth! Thus before every far reaching human advance, circumference and 

 centre will forever retreat. 



Norman Wiard, Esq., on invitation, presented the following paper, to 

 which he added explanatory remarks. 



Great Guns. 



1. Since the battle of Solferino, when^rifled cannon were first actively 

 put in use, all the nations liable to a state of war have been straining every 

 nerve to improve their ordnance, and hence their improvements in the 

 means of defense, and the experi . ents conducted to produce large rifled 

 guns were cotemporary with the experiments in ironclad ships. Modern 

 warfare, therefore, with large rifled guns and iron-clad ships, is in its 

 infancy, although large smooth bores and wooden ships have an earlier 

 date; their general use in service began with the present rebellion, and, at 

 this date, the large gun of eitlier class, not liable either to the accident of 

 enlargement of the bore or bursting has not yet been made; while of rifles 

 we have none over 30-pounders that have not proved utterly unsafe, except 



