The Long Tom was a device shaped like a long trough, used in the alluvial mining of gold. Its use evolved as an extended version of the rocker in the mid 1800s and its broad application took off during the California Gold Rush. The Long Tom featured a long washing box with a perforated screen to catch larger-sized rocks and debris, and under the screen, a riffle or sluice board to trap gold.
[edit] History
Long Toms were used for the small-scale mining of gold by prospectors known as the forty-niners, beginning in late 1848 just as the California Gold Rush was taking off. At that time, it took about six to eight men to exploit the operation of the Long Tom to its fullest potential.[1] By 1850, it had been widely adopted and was used in combination with hydraulic mining similar to sluices, the forerunner of the Long Tom. The pairing of Long Toms with hydraulic mining caused such environmental damage the the practice was eventually banned, marking one of the earliest environmental laws in U.S. history.[2]
[edit] Process
Long Toms consisted of different components. A short receiving box, also called a launder, was placed at the front and used to take in gravel. Underneath this box was a longer, open, trough-shaped box varying in length from six to 20 feet (1.8 to 6.1 m), used for washing the gravel. Near the lower end of the wash box was a perforated screen or plate set at an angle; set underneath it was a short sluice box with riffles. Long Toms were usually staggered on a set of slopes with a one- to one-and-a-half-foot (0.3 to 0.5 m) drop between each. The Long Toms were spaced apart this way to assist in breaking up clay and releasing gold.[3] A constant flow of water washed and forced the gravel out of the receiving box into the washing trough. The action of the water enabled the gold to sink to the bottom of the gravel layer. Material less than an inch (2.5 cm) in diameter was released through a plate or screen at the end of the washing trough and into a riffle box. Finer gold was caught by the riffles in the riffle box. The finer gold was separated from ore concentration by panning. Another method was to amalgamate the gold using mercury, though this was considered highly dangerous and toxic.[4] Twice daily, the gold would be caught inside the riffles, removed, and panned.[5]
It typically took up to four men to operate a Long Tom. Two men would shovel the gravel into the receiving end of the device and another miner would be required to remove larger rocks with a shovel or twined pitch fork from the trough as the material was forced downwards by the stream of water and gravity. A fourth man would shovel away the small rocks from the lower end of the Long Tom.
One of the disadvantages of using Long Toms is that they demanded a continuous source of fast-moving water. This often meant Long Toms were placed in close proximity to the riverbank. Sometimes ditches had to be dug to deliver water from a source directly to the mining site. Paddlewheels were even used to direct the supply of water towards Long Toms. Some of the first ditches dug in California were used for this purpose. Some of these ditches still exist and are now used for agriculture.[6]
[edit] References
- ↑ California Gold Mining Techniques: The Long Tom. Andrea Franzius. Duke University. 2008-12-02.
- ↑ Using the Long Tom in gold mining. John Carter. Helium. 2008-12-02.
- ↑ Small Mining. Long Tom. Alluvial Exploration and Mining. 2008-12-02.
- ↑ The Long Tom. Sierra Nevada Virtual Museum. 2008-12-02.
- ↑ Using the Long Tom in gold mining. John Carter. Helium. 2008-12-02.
- ↑ Early Gold Mining Methods. Sierra Foothill Magazine. 2008-12-02.
