Cows in milking shed waiting for vacuum milker to be attached. Large dairy in Tom Green County, Texas by Russell Lee https://www.rawpixel.com/image/12147274/image-cow-person-artFree Image from public domain licenseRotary vacuum filter used for removing cyanide solution containing gold from the tailings. Gold mine at Mogollon, New Mexico… https://www.rawpixel.com/image/12173163/image-person-art-vintageFree Image from public domain license[Untitled photo, possibly related to: Rotary vacuum filter used for removing cyanide solution containing gold from the… https://www.rawpixel.com/image/12171650/image-art-vintage-goldFree Image from public domain license[Untitled photo, possibly related to: Rotary vacuum filter used for removing cyanide solution containing gold from the… https://www.rawpixel.com/image/12171415/image-art-vintage-goldFree Image from public domain license