which - behold! - will throw up sparks like [burning] logs,
 - Mohammad Asad
throwing up sparks as huge as castles,
 - Muhammad Farooq-i-Azam Malik
Indeed, it hurls sparks 'as big' as huge castles,
 - Mustafa Khattab
Lo! it throweth up sparks like the castles,
 - Marmaduke Pickthall
"Indeed it throws about sparks (huge) as Forts 5878
 - Abdullah Yusuf Ali
Qasr: Fort, big building, palace. An alternative reading is Qasar, plural of Qasarat (-un), meaning bundies of wood used for fuel: Ibn Abbas apud Bukhari. I almost prefer this latter reading.