History:
Constructed in 1856 to manufacture lead shot ammunition, the Shot Tower is one of only a few remaining shot towers in the United States, and the only one west of the Mississippi River. The 120-foot Shot Tower produced lead shot from 1856-58, and then was closed. It was briefly refurbished for use during the first year of the Civil War. It was used by the Standard Lumber Company as a fire watchtower from the late 1880s until the company was destroyed in the 1911 lumberyard fire. The tower stood deserted in its post-fire ruin from 1911 to 1959. The 1911 fire destroyed the original wooden stairs, leaving no ready means to access the tower interior for maintenance and repairs. The tower stood roofless until a concrete cap with a hatchway was added to the tower in 1960 and replacement brick was used to reconstruct the lost upper portion of the top floors.
Lead Shot Production Process:
A simple sounding invention, Shot Towers relied on the laws of physics and used gravity to do the heavy lifting to form its product. At the top of the tower there is a mesh grid through which molten lead is poured. As it falls, the lead drop is turned, stretched, and pulled tight and smooth into a near perfect sphere. The fall takes seconds and at the end it drops into a pool of water to rapidly cool into its resting shape.
At its peak, records indicate that up to 8 tons of shot was produced herer daily and could range from the common .69 caliber rounded musket ball to this heavyweight measuring almost 2 inches across. A lead shot like this would likely be used for cannon cannister fire.
Construction:
The Shot Tower consists of a tapered square-cut masonry hollow column form. The whole structure stands 120'5" above the current ground level. Seven stories (82’11”) are of Galena Dolemite stone construction, and the uppermost three stories (37’6”) are built of soft red brick.
There is strong evidence that some of the originally exposed column base is now buried, as is an estimated 15-20 feet of stone foundation. The load-bearing masonry walls are progressively reduced from a base width of three feet to just one foot at the top of the tower. The base measures 19’2” square, while the cap measures 12’4” square. The square interior shaft is a consistently square 13’2” x 13’2”.
Geology of the Tower:
The first seven stories of this tower are Galena Dolemite stone. Dolomite is very economically valuable. As its properties are similar to those of limestone, in places where limestone is unavailable or more costly, we often process dolomite stone to produce most building materials, such as road base materials, concrete and asphalt aggregates, ballast, cement, etc. Many people think that dolomite and limestone are very similar, as they are both sedimentary carbonate rocks with similar appearances and uses. Dolomite rock (dolostone) is often found along with limestone but there are some major differences:
- The amount of magnesium contained. Dolomite mineral is a calcium magnesium carbonate mineral (dolomite) with a calcite content of less than 5%. However, limestone is a calcium carbonate mineral made of calcinate (CaCO3).
- Dolomite is harder than limestone (2-4 on Mohs hardness).
- Sand, clay and silt are commonly found in limestone as impurities but not quite common in dolomite.
- Dolomite will not bubble when introduced to acid, while limestone readily reacts with hydrochloric acid to produce CO2.
- Unlike limestone, dolomite is insoluble in water, resistant to various external damage, and has a shiny surface.
- Dolomite is cheaper than limestone.
In order to log this Earthcache please answer the following questions:
1) At the base of the tower how would you descibe the texture of the dolomite rock? (smooth, rough, bumpy, gritty, lumpy, etc...)
2) Dolomite exhibits a variety of colors. Common colors include white, gray, pink, and reddish-white, with variations often attributed to impurities. What colors of dolomite do you see on the tower?
3) Please include a photo of you or a signature item with the tower.
Sources:
https://www.cityofdubuque.org/712/Shot-Tower
https://www.cityofdubuque.org/DocumentCenter/View/2526/Shot-Tower-Rehabilition?bidId=
https://en.wikipedia.org/wiki/Shot_Tower_(Dubuque)
https://www.ftmmachinery.com/blog/what-is-dolomite.html