358 Mr. Carmichael on the [Nov, 



atmospheres, which will become sensible when the temperature 

 of the surrounding medium is lowered, the intensity of which, as 

 well as its extent, depending upon the force with which the body- 

 attracts caloric ; this is the cause why the temperature is less in 

 the higher regions of the atmosphere than near the earth's sur- 

 face ; for the earth is a warm globe placed in a region of absolute 

 cold. 



Prop. 9 and 10 immediately apply to the curious phenomena 

 of unannealed glass, and some other similar substances. If the 

 force of cohesion be very great, the particles of the body may 

 form such an arrangement that straight lines which join their 

 centres form squares, and a considerable additional increment of 

 heat required to separate them. In this situation of the atoms, 

 the body will be in a semifluid state, and if cooled, this arrange- 

 ment will remain, by prop. 9, if no disturbing force operate ; but 

 if but one particle be disturbed when the mass is cold, the equi- 

 librium, and consequently the arrangement of the whole system 

 is destroyed. Now glass is a substance which is in this semi- 

 fluid state when fused, and which, when cold, has great cohe- 

 sive force ; and if cooled very gradually, the particles will assume 

 a state of permanent equihbrium, by prop. 10; but if rapidly 

 cooled, the intensity of the cohesive force will prevent this, and 

 preserve the arrangement in which the particles were placed 

 when in a state of fusion ; when by prop. 9, any force disturbing^ 

 some of the atoms, the whole system is deranged, which must 

 produce a fracture of the mass in so hard and brittle a substance. 



The primary laws of the radiation of heat and of crystaUization 

 are now easily explained. These will be investigated in the 

 next. 



(To be continued.) 



Article V. 



An Essay on the Invention of Alphabetic Writing.* 

 By A. Carmichael, M.R.I.A. 



The difficulty of accounting for the invention of alphabetic 

 writing, and the impossibility of tracing any connexion between 

 letters, which are the representatives of sounds, and hieroglyphics, 

 which are resemblances of things, has induced men of extraor- 

 dinary erudition and talents to ascribe the gift to a direct revela- 



• This essay was published in a late volume of the Memoirs of the Royal Irish 

 Academy. We have inserted it in the Annals of Philosophy to show the coincidence 

 of the sentiments with those of Mr. Turner, of which an account was given in the 

 review of the last vulunie of the Manchester Memoirs in vol. xv, p. 193, of the 

 Annals of Philosophy. 



