This month we are taking a look at another man you have likely never heard of, yet he also was honored by having a unit of electrical measurement named after him. He is the first American I have written about so far, and as you can see from the timeline, he was a contemporary of Michael Faraday. This month I am introducing you to Joseph Henry (1797- 1878). It occurs to me that perhaps Faraday and Henry are less well known because the units named after them, the farad and the henry, are not as well-
known as the volt or the watt. In electronics, there are three primary passive building blocks or components: resistors, capacitors, and inductors. Passive means that they can function without any external power source. By contrast, vacuum tubes, transistors and IC's are all active components as they require external power sources to operate. Resistors, measured in ohms, resist the flow of current, and that resistance remains essentially unchanged regardless of the type of current trying to pass through it. Direct current, low-frequency alternating current and high frequency alternating current all are equally attenuated by resistors. Capacitors and inductors behave differently from resistors in many ways, but basically, these components behave in a frequency dependent way. Capacitors measured in farads, do not pass direct current at all and so they have an extremely high resistance at DC. At high frequencies, however, the resistance of the capacitor drops considerably so high frequencies pass through unopposed. The inductor measured in henrys is exactly opposite from the capacitor. The inductor passes DC quite easily with virtually no resistance. As the frequency rises, so does the resistance. These two tools along with the resistor are at the heart of all filters or any circuit where you want different behaviors at different frequencies. But I digress…. back to Joseph Henry!
Joseph Henry was born on December 17, 1797, in Albany New
York. His parents William Henry and Ann Alexander had recently emigrated from Scotland. William was a day laborer on the Hudson River boats and was often in very poor health. Some sources say he was likely an alcoholic. Hoping for a better life for her son, Ann sent Joseph to live with relatives in Galway, New York when Joseph was seven years old. Joseph’s father died two years later. Joseph attended school in Galway, but at age 10 he started working in a general store to help make ends meet. Like his father, Joseph was frequently in poor health and was what some biographers called “a delicate child”.
At age 13 Joseph moved back to Albany to help his mother. He had a job as an apprentice to a watchmaker for about two years, but due to the failing economy of Albany, the shop closed. His mother took in boarders to help pay the bills and it was one of these borders who was to essentially change Josephs’ life. The border, named Boyle, loaned Joseph a book called Lectures on Experimental Philosophy, Astronomy and Chemistry Intended Chiefly for the Use of Young People.
Joseph became obsessed with this book, so much so that Boyle told Joseph that he could keep the book. Many years later Joseph wrote in the back cover
“This book, although by no means a profound work, has, under Providence, exerted a remarkable influence on my life. It accidentally fell into my hands when I was about sixteen years old and was the first book that I ever read with attention. It opened to me a new world of thought and enjoyment; invested things before almost unnoticed with the highest interest; fixed my mind on the study of nature, and caused me to resolve at the time of reading it that I would immediately commence to devote my life to the acquisition of knowledge.” Joseph Henry 1837.
Soon, Joseph was teaching in local schools to earn some money. By 1819 he had earned a reputation as a very bright young man and he was offered free tuition at Albany Academy. He studied math, chemistry, and physics and graduated in 1822. After a short stint working with a civil engineer, he returned to Albany Academy in 1826 as an assistant teacher and in two years, at the age of 31, he was promoted to Professor of Mathematics and Natural Philosophy. At Albany, Henry was in a position to do basic research. He had always been interested in the earth's magnetic fields and this interest in magnetism is what influenced him to investigate electricity and magnetism. A British inventor named William Sturgeon had built the world's first electromagnets in 1825. When Henry heard of Sturgeons’ invention, he was fascinated and built his own with which to experiment. Soon he was looking for ways to make them significantly more efficient. By 1830, Henry demonstrated the world most powerful electromagnet lifting 750 pounds! To put this into perspective, before 1830 the record for the most weight lifted by an electromagnet was 9 pounds! By 1831, Henry had developed an electromagnet capable of lifting more than 2000 pounds and in a few years, this number increased to 3300 pounds. But Henry did much more than focus on building powerful electromagnets. In 1830 he demonstrated to his students the first electric bell, which he could ring from about a mile away, basically showing two potentially useful devices; the doorbell and the telegraph. He also showed a crude example of the world’s first relay, a sort of remote-controlled switch. Because he thought of himself as a pure scientist, he never tried to patent anything. Others, however, saw incredible potential in what Henry had demonstrated. One of Henrys’ colleagues at Albany told Samuel Morse of Henrys’ work, especially the relay as he realized that the relay was the missing link that would make long-distance telegraphy possible. Morse had already been working independently on a telegraph system using devices much like the ones developed by Henry but was looking for a way to extend the distances. Henrys’ relay was exactly what Morse was looking for. Henry cooperated with Morse and within a decade or so, Morse had patented the telegraph and was sending messages over great distances, and of course, made himself a considerable fortune in the process. Over time Henry became resentful that Morse did not really acknowledge his role in the development of the telegraph.
Possibly most significant is the work that Henry did on induction. He actually discovered mutual induction about the same time that Faraday did, possibly even before Faraday. But Faraday published his results first and therefore is credited with the discovery. His years at Albany were to be his most productive years in terms of his discoveries and inventions. In 1833 Henry was invited to take a position at the College of New Jersey, now known as Princeton University. This was a significant step up in prestige, but the responsibilities of a Professor at Princeton made it difficult to do as much basic research as he would have liked. Still, he managed to continue his research on induction, publishing a very important work in 1838 called Electro Dynamic Induction,
which expanded on the work first published by Faraday. Henry also worked on the detection of the Earths’ magnetic fields, as well as developing a method to measure the temperature of sunspots. Henry remained as Chair of Natural History at Princeton until 1846 when he became the first secretary of the newly founded Smithsonian Institution.
Even though it is not directly related to the story of Henry, the history of the formation of the Smithsonian Institution is worth telling. James Smithson an English gentleman of fortune, and a notable chemist in his own right died in 1829 leaving only one heir, a nephew. When Smithson’s will was opened, it was short and to the point. He left an annuity to his loyal servant and the rest of his considerable estate to the nephew. It also contained an interesting clause. If the nephew were to die without heirs, the entire estate was to be left “to the United States of America, to found at Washington, under the name of the Smithsonian Institution, an establishment for the increase and diffusion of knowledge among men”.
Why Smithson did this is not known. He never traveled to the US and his friends and colleagues were unaware of any particular fondness for the US, nor did Smithson have any contacts in the US. His nephew was unmarried and in very poor health and died in 1835 without putting a significant dent in the fortune. After some wrangling by the lawyers for the estate, the money amounting to about a half million dollars was deposited into the US treasury in 1838. Adjusted for inflation, that would be around 17 million in today's money, however, in 1838, a half million dollars was about 1/66 of the national budget! That would be in the neighborhood of 7 billion today. Here is where the story gets all too familiar. Congress
had to now figure out what to do with this sizable chunk of money. What exactly does “an establishment for the increase and diffusion of knowledge among men”
mean? It took 8 years to figure it out. First, there were strict constructionists who argued that the US government had no authority to accept such a bequest and the money should be sent back to England. One member of Congress suggested that it should be used for an agriculture school. Another said it should be used for the “prosecuting (i.e. the pursuit) of physical experiments”. Yet another said it should be used “for the instruction of females”. The Columbian College was certain that it
should be the recipient of the money. John Quincy Adams wanted to establish a great astronomical observatory. Another pushed for the money to be given to the National Institute for the Promotion of Literature and Science. Mr. Espy, a meteorologist, wanted the money for meteorological observations across the country. Another lobbied that the sum be used for a farm school. Fortunately for us, they figured it out, even though it took eight years! President Polk signed the Smithsonian Act into law in August of 1846. On December 3 of the same year, a man who was considered the preeminent American scientist of the day, Joseph Henry, was elected to the position of Secretary of the Smithsonian Institution. He remained in that position until his death at age 80 in 1878 and is largely responsible for setting the foundation for the institution it was to become. Today the Smithsonian is the largest museum, education, and research facility in the world.
I think is it interesting to compare the lives of Henry and Faraday. They were both born in poverty, they both had fathers who were in poor health and often could not work. They both became apprentices, they were both inspired to pursue the sciences because of books they chanced upon as adolescents. They became lab assistants. They both were devoutly religious, and they both made contributions to electromagnetism at the same time. They both saw themselves as pure scientists and others made fortunes on their discoveries.
In 1893 the henry was adopted as the unit of inductance, the only unit named after an American.