On the different Theories of Arches, Vaults, &c. 409 



earthly beings that I now confine myself) must have an 

 affinity to a grosser and more impertect substance. We 

 have no idea of any other than what is called matter; but 

 this is not to say that no oiIkt does exist. I have sup- 

 posed the soul to be a subtile ethereal substance, because 

 SEther is the most subiile refined substance of which we 

 have any idea : 



" Vast chain of being', v/hich from God bejr-n; 

 Natures etiiertal, huniaii; — ai«-<fl, — Alan." 



'^ At the height of four thousand miles," says Bentley, 

 " the cether is of that wonderful tenuity, that if a sniall 

 sphere of common air of an inch diameter sb.oidd be ex- 

 panded to the thinners of thai cetiier, it would more than 

 take up the orb oi'Siturn, which is many million times big- 

 ger tiian the Earth." if this be true, it surely is not extra- 

 vagant to suppose that God can endow matter still more 

 subtile with the attributes of mind ; and make such matter 

 indivisible, incorruptible, and immortal. 1 can and do 

 suppose, that what we call soul is formed of such matter; 

 that all animals possess a sou! ditlerentiy tenuous; and that 

 the su|)eriority of man to the hiwer animals, and the dispa- 

 rity of intellect wliicii exists between individuals of the 

 human and brute species, are owing to ihis dilleience of 

 tenuity, which may be increased or diminished by the neg- 

 lect or exercise ot the faculties, and the nivslenous operation 

 of physical causes. 



LXXV. Some Accoiail of the different Theories of Arches 

 or f'auili, (Did cf Duriies, and of the yluthors who have 

 written on ihis ino>t deticu/e and important yjpplicalion 

 of Mathematical Science. By a Cokrkspondent. 



[Ciincliided from p. 39!.] 



.1 HE theory of domes and their tambour walls may be eli- 

 cited in the same manner as that of arches and piers, with 

 some exception. It is to be recollected that, in the arch, 

 before .Tnv voussoir can fall, the lov» er voussoir must rise out- 

 wards or descend inward, so as to let the centre of pressure 

 of the upper free, inlern.illy or externally : but in a dome, 

 .as not any voussoir can descend inward, by reason of its 

 being one, in a svstem of voussoirs in equilibration, which 

 is one ring of the dome ; the dilapidation can only arise 

 from the centre of pressure being freed exiernally : hence 

 curves concave outwards are ap|)licable to domes, and the 

 (ic»me does not require a crown, each successive ring formmg 



a key- 



