▁where ▁Thomas ▁Kir by ▁first ▁introduced ▁the ▁process ▁for ▁British ▁da iry ▁her ds . ▁ ▁The ▁modern ▁sil age ▁preserved ▁with ▁acid ▁and ▁by ▁prevent ing ▁contact ▁with ▁air ▁was ▁invent ed ▁by ▁a ▁Finn ish ▁academic ▁and ▁professor ▁of ▁chem istry ▁Ar tt uri ▁Il m ari ▁V irt an en . ▁V irt an en ▁was ▁awarded ▁ 1 9 4 5 ▁Nobel ▁prize ▁in ▁chem istry ▁for ▁" for ▁his ▁research ▁and ▁invent ions ▁in ▁agricult ural ▁and ▁nut r ition ▁chem istry , ▁especially ▁for ▁his ▁f od der ▁pres ervation ▁method ", ▁pract ically ▁invent ing ▁modern ▁sil age . ▁▁ ▁Early ▁sil os ▁were ▁made ▁of ▁stone ▁or ▁concrete ▁either ▁above ▁or ▁below ▁ground , ▁but ▁it ▁is ▁recognized ▁that ▁air ▁may ▁be ▁sufficiently ▁ex cluded ▁in ▁a ▁tight ly ▁pressed ▁stack , ▁though ▁in ▁this ▁case ▁a ▁few ▁inches ▁of ▁the ▁f od der ▁round ▁the ▁sides ▁is ▁generally ▁useless ▁ow ing ▁to ▁mil de w . ▁In ▁the ▁U . S . ▁structures ▁were ▁typically ▁constructed ▁of ▁wooden ▁cyl ind ers ▁to ▁ 3 5 ▁or ▁ 4 0   ft . ▁in ▁depth . ▁ ▁In ▁the ▁early ▁days ▁of ▁mechan ized ▁agricult ure , ▁stal ks ▁were ▁cut ▁and ▁collected ▁manually ▁using ▁a ▁kn ife ▁and ▁hors ed ra wn ▁w agon , ▁and ▁fed ▁into ▁a ▁station ary ▁machine ▁called ▁a ▁" s ilo ▁fill er " ▁that ▁cho pped ▁the ▁stal ks ▁and ▁ble w ▁them ▁up ▁a ▁narrow ▁t