Aderaid na feallsamain co fuilit tri gluasachta ann .i. gluasacht o meadhon & gluasacht cu meadhon & gluasacht a timcill medhoin.
Is e is gluasacht o medhon ann .i. an gluasacht teit o talmain amach co cotrom d'innsaighe gach uile rainn don cercaill timcill. Is e as gluasacht cu medhon ann an gluasacht teit sis on cercaill timcill co talmain . Is e as gluasacht a timcill mhedhoin ann .i. an gluasacht noch gluaises da rer na cercaille timcill & is o na primhgluasachtaibh sin genter gach uili gluasacht ele da fuil is an domhan & is dib sin gluasacht na ceithre dula, oir gluaisidh cuid aca o meadhon & cuit co meadhon & ni gluaisind en raed co nadurtha a timcill medoin acht an firmaminnt na rann da rannaibh. An da duil gluaises cu medhon .i. talman & uisci, as luaithi an gluasacht co medhon talmain na an uisci. Don da duil gluaisis o medhon .i. aer & teine is luaithe gluaises in teine o medhon na'n t-aer. Et is mar sin atait na duili gluaises go medhon trom & na duili gluaises o medhon etrom. Et tuictear mar congluais
D'foillsiugad an adbair so nis mo dagen fidair annso this scailfis amach brig na raiteadh so. Dagen ar dus fidair na talman & is i so i & scribfad A 'na meadhon & curfead B litir 'na mullach & daden 'na dedaidh sin cercall na firmaminti a dimcill na talman & cuirfed C 'na oirrcher & D 'na mullach & E 'na h-iartar & F 'na h-ichtar & ar cuma na fidrach atait da corp do na corpaid duilidhi noch gluaises o medon ann na cercaille timcill .i. o A go B & is iat sin tine & aer. Et atait an da corp ele gluaises on cercaill timcill go medhon .i. o B go h-A & is iat sin talam & uisci. An treas primgluasacht ata ann .i. gluasacht do rer an cercaill timcill & is e sin gluasacht na firmaminnti & is amlaid gluaises o C go D & o D go E & o E go F & o F go C & is leor sin do na h-eolcaib.