I think it's <span>In the early 1930s, as the nation slid toward the depths of depression, the future of organized labor seemed bleak. In 1933, the number of labor union members was around 3 million, compared to 5 million a decade before. Most union members in 1933 belonged to skilled craft unions, most of which were affiliated with the American Federation of Labor (AFL).
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Answer:
It wasn't until 1874, when Illinois farmer Joseph Glidden emerged victorious from patent battle over a mechanically-produced fencing material that barbed wire could be made at scale. Glidden's machine pulled two strands of wire tight around the barb, then wound the wires together around the regularly-spaced spikes.
Explanation:
got this from google which is accurate to your question
Surely only a few of us know that many modern high-school-level concepts in mathematics first were developed in Africa, as was the first method of counting. More than 35,000 years ago, Egyptians scripted textbooks about math that included division and multiplication of fractions and geometric formulas to calculate the area and volume of shapes (3). Distances and angles were calculated, algebraic equations were solved and mathematically based predictions were made of the size of floods of the Nile. The ancient Egyptians considered a circle to have 360 degrees and estimated Π at 3.16 (3).
Eight thousand years ago, people in present-day Zaire developed their own numeration system, as did Yoruba people in what is now Nigeria. The Yoruba system was based on units of 20 (instead of 10) and required an impressive amount of subtraction to identify different numbers. Scholars have lauded this system, as it required much abstract reasoning (4).
Astronomy
Several ancient African cultures birthed discoveries in astronomy. Many of these are foundations on which we still rely, and some were so advanced that their mode of discovery still cannot be understood. Egyptians charted the movement of the sun and constellations and the cycles of the moon. They divided the year into 12 parts and developed a yearlong calendar system containing 365 ¼ days (3). Clocks were made with moving water and sundial-like clocks were used (3).
A structure known as the African Stonehenge in present-day Kenya (constructed around 300 B.C.) was a remarkably accurate calendar (5). The Dogon people of Mali amassed a wealth of detailed astronomical observations (6). Many of their discoveries were so advanced that some modern scholars credit their discoveries instead to space aliens or unknown European travelers, even though the Dogon culture is steeped in ceremonial tradition centered on several space events. The Dogon knew of Saturn’s rings, Jupiter’s moons, the spiral structure of the Milky Way and the orbit of the Sirius star system. Hundreds of years ago, they plotted orbits in this system accurately through the year 1990 (6). They knew this system contained a primary star and a secondary star (now called Sirius B) of immense density and not visible to the naked eye.
Metallurgy and tools
Many advances in metallurgy and tool making were made across the entirety of ancient Africa. These include steam engines, metal chisels and saws, copper and iron tools and weapons, nails, glue, carbon steel and bronze weapons and art (2, 7).
Advances in Tanzania, Rwanda and Uganda between 1,500 and 2,000 years ago surpassed those of Europeans then and were astonishing to Europeans when they learned of them. Ancient Tanzanian furnaces could reach 1,800°C — 200 to 400°C warmer than those of the Romans (8).
