The long tom functioned similarly to the rocker but increased its efficiency. It also had the shape of a trough, but it was much larger, 12 to 15 feet long and about 2 feet wide. Mainly made out of wood, it had a metal bottom with a sieve and a ripple box at its end. This machine was put up with a slight slope, thus facilitating the water flow.
While one man shoveled dirt into the long tom, making sure that the water was running, another mixed water and dirt while taking out big stones that could damage the sieve. At the end of the day, the dirt was taken out of the box and washed in a pan. Six to eight men had to work a long tom to fully exploit its capacities. A few miners started to employ the long tom at the end of 1848, and by 1850 it became a common machine.