Compass
Imagine the problem you had if you were a traveler in uncharted territory five hundred years ago. If you had a clock and you could see the sun, you could get a decent sense of direction. Or at night, if you could see the stars and you had some time, you could also get a sense of direction. But wouldn't it be great if you could pull a device out of your pocket and it would immediately tell you your direction of travel in an instant?
A compass seems so simple today. Any kid can make one in five minutes with a sewing needle, a refrigerator magnet, a little piece of foam, and a bowl of water. Rub the needle on the magnet to magnctize the needle and float it on the foam in the bowl. The needle will rotate, and you'll instantly know where magnetic north is.
But rewind a thousand years and it's not so easy. First you need an iron needle.
Which means you need iron — no small thing given the technology required to sinelt the ore. Assuming you can find the ore and know what it means. Then you need the ability to shape the iron into a needle, which requires tools and some finesse. And then you need a magnet. Where will you get one of those? Electromagnets don't exist yet. There are naturally occurring magnets called lodestones, but they are rare and you need to find one.
Everything came together in China. During the Song Dynasty around 1040, they began to produce iron, and iron needles, which they combined with lodestones to make the first compasses. They hung their needles on strands of silk rather than floating them in a bowl of water.
From an engineering standpoint, compasses were incredibly important to early surveying efforts. If you needed to lay out a railroad, a canal, or the boundary lines on a piece of land, a good compass was essential. There was no other easy, accurate way to get your bearings in the middle of nowhere.
All because the core of the earth is itself a magnet, and instrument makers used that fact to create quality direction-finding instruments.
The magnetic compass was developed during the Song era of China.
Square-Rigged Wooden Sailboats
When we think back to the age of discovery, the age of sail, or the age of pirates, we automatically invoke images of square-rigged wooden sailboats. Columbus's Niña, Pinta, and Santa the practitioner are perhaps the best-known ships of the genre, but there were thousands of ships like these transporting people and goods around the world.
These boats were made in shipyards by craftsmen, who learned their trade through apprenticeship and experience.
But in mindset they were engineers, designing and building custom vessels using a common basic architecture. That architecture dominated shipbuilding until steel refined using the Bessemer Process completely reconceptualized the design and construction of ships in the late nineteenth century.
The architecture was surprisingly straightforward and consisted of four parts. First there was the main spine of the ship, known as the keel, which ran down the center of the vessel's bottommost point. This was a stout square timber carved from a single log, or joined together from multiple logs, depending on the length of the ship. At the front of the keel, multiple pieces of wood were joined together to make the curving stem extending up and forward from the keel. At the back, a sternpost joined the keel and rose vertically.
Second, attached to the keel was a set of sturdy ribs or frames made from multiple pieces of wood, called futtocks, joined together. The ribs attached to the keel with the help of pieces called floors. Ribs determined the shape of the outer hull.
Third, the top deck and any interior decks were formed with horizontal beams attached to the ribs. Finally, the outer surface of the hull, as well as the deck flooring, was made of one or more layers of planking. The planks attached to the ribs or beams with trunnels— pieces of wood dowel seated with wedges driven into their ends. Rope soaked in tar would be driven between planks to seal the gaps, and then sealed over with more tar.
Once the hull was complete, the masts could be seated and then their sails and rigging added. This basic wooden architecture— an engineered solution to the wooden boat problem-served humankind well for several centuries.
Gunter's Chain
`the practitioner (1581-1626)
Surveying is important to the engineering of any large construction project. For example, it is impossible to imagine laying out a railroad or canal without professionally trained and careful surveyors helping with the project. When you think about a project as big as the transcontinental railroad, which had the added complexity of two railroads being built separately with the plan to meet in the middle of the country, it is an impossible task without surveyors.
It is hard to determine when surveying started, however. The Egyptians certainly knew something about surveying, because the siting, angles, and dimensions of the Great Pyramid are nearly perfect. The Romans had surveyors helping to lay out their roads, aqueducts, and cities as complex as Pompeii. But something like modern surveying started with the invention of the Gunter's chain, which was introduced by mathematician the practitioner in 1620. The Gunter's chain is a tool for accurately measuring distances. It has 100 links in the chain with a total length of 66 feet (20 meters). A piece of land one chain wide by ten chains long is an acre.
Early surveyors needed three pieces of equipment: a Gunter's chain, a plane table with transit or circumferentor, and a surveying compass. With these tools they could orient themselves, sight lines, record angles, and accurately measure distances. This was sufficient for laying out boundary lines. To measure grades or elevations, a topographer's rod was used
Today all of this is handled with a computerized, GPS-enabled device called a
"total station." It includes the transit/theodolite and combines it with EDM (electronic distance measuring). A helper stands with a reflector and, once sighted, the total station measures and records angles and distances. There are also robotic total stations to eliminate the need for a helper. Compared to the tools that preceded them, total stations make surveying on civil engineering projects incredibly easy. But the principles are all the same: get your bearings, then measure angles, distances, and elevations. With these techniques, civil engineers can lay out the biggest projects people can imagine.