ine ar ▁transmission ▁of ▁light ▁as ▁well ▁as ▁the ▁movement ▁of ▁light ▁through ▁solid ▁objects . ▁He ▁uses ▁a ▁met ap hor ▁of ▁wine ▁flow ing ▁through ▁a ▁v at ▁of ▁g rap es , ▁then ▁exit ing ▁through ▁a ▁hole ▁at ▁the ▁bottom ▁of ▁the ▁v at . ▁Now ▁consider ▁that , ▁since ▁there ▁is ▁no ▁vac u um ▁in ▁Nature ▁as ▁almost ▁all ▁the ▁Philosoph ers ▁aff irm , ▁and ▁since ▁there ▁are ▁never theless ▁many ▁por es ▁in ▁all ▁the ▁bodies ▁that ▁we ▁perce ive ▁around ▁us , ▁as ▁experiment ▁can ▁show ▁quite ▁clearly , ▁it ▁is ▁necessary ▁that ▁these ▁por es ▁be ▁filled ▁with ▁some ▁very ▁subt le ▁and ▁very ▁fluid ▁material , ▁extending ▁without ▁inter ruption ▁from ▁the ▁stars ▁and ▁plan ets ▁to ▁us . ▁Thus , ▁this ▁subt le ▁material ▁being ▁compared ▁with ▁the ▁wine ▁in ▁that ▁v at , ▁and ▁the ▁less ▁fluid ▁or ▁heav ier ▁parts , ▁of ▁the ▁air ▁as ▁well ▁as ▁of ▁other ▁transparent ▁bodies , ▁being ▁compared ▁with ▁the ▁bunch es ▁of ▁g rap es ▁which ▁are ▁mixed ▁in , ▁you ▁will ▁easily ▁understand ▁the ▁following : ▁Just ▁as ▁the ▁parts ▁of ▁this ▁wine ... t end ▁to ▁go ▁down ▁in ▁a ▁straight ▁line ▁through ▁the ▁hole ▁[ and ▁other ▁holes ▁in ▁the ▁bottom ▁of ▁the ▁v at ] ... at ▁the ▁very ▁instant ▁that ▁it ▁is ▁open ... without ▁any ▁of ▁those ▁actions ▁being ▁imp eded ▁by ▁the ▁others , ▁nor ▁by ▁the ▁resistance ▁of ▁the ▁bunch es ▁of ▁g rap