Learning Science in 1879
By: Don Cross
Tags: Astronomy, Education, History, Science, Physics

Fun with Dead Bodies

Science is a human endeavor, and as such, it has a darker side. Mary Shelley published her horror classic Frankenstein in 1818. The Quackenbos textbook recounts a real-life experiment that may have been inspired by Shelley’s disturbing fantasy. In the section titled “Physiological Effects of Voltaic Electricity,” the author recounts:

A few years ago, the body of a murderer hanged in Glasgow was subjected, about an hour and a quarter after his execution, to the action of a battery consisting of 270 pair of four-inch plates. One pole was applied to the spinal marrow at the nape of the neck, and the other to the sciatic nerve in the left hip, when the whole body was thrown into a violent tremor as if shivering with cold. On removing the wire from the sciatic nerve to a nerve in the heel, the leg was thrown out so violently as nearly to overturn one of the assistants, who tried in vain to prevent its extension. On directing a current to the principal muscle of respiration, the chest heaved and fell, and labored breathing commenced. When one of the poles was applied to a nerve under the eyebrow and the other to the heel, the most extraordinary grimaces where produced.

The text goes on to recount the different ways the experimenters were able to contort the dead man’s face by placing electrodes in different locations about the head.

I don’t fault the author of a science textbook any opportunity to capture the attention of readers. The effects of electricity on animal tissues are fascinating and important. These phenomena led to our modern understanding of how nerves make our muscles move and relay our sensations into the brain.

But I can’t help but wonder about the motivations of the Glaswegian experimenters. It’s not clear to me that they learned anything new from their ghastly experiment. A century earlier, Luigi Galvani already had discovered chemically-induced electricity causes dead frogs’ legs to twitch. I suspect the post-execution body zapping was just for fun. Alcohol may have been involved.

The Victorian Heat Ray

It is clear that Quackenbos understood infrared radiation, although I can’t find the word infrared anywhere in the text. Instead, he uses the term radiant heat. As we see in the following diagram and text, scientists in 1879 understood that an invisible form of light could be transmitted through space and concentrated by parabolic mirrors.

Apparatus for remotely igniting a target with infrared radiation.

Quackenbos writes:

The reflection of radiant heat may be illustrated with the apparatus represented in Fig. 213. A and B are concave metallic mirrors, highly polished. In the focus of A is placed a red-hot ball C. This ball radiates heat in all directions, and some of its rays strike the mirror A, from which they are reflected in parallel lines to B. By B they are again reflected and brought to a focus at D, where a thermometer indicates a rise of temperature. Sufficient heat may thus be concentrated at D to set fire to phosphorus or gunpowder.

So here we have a device that sends an actual heat ray through the air and sets fire to a remote object! It’s not as impressive as a modern steel-cutting laser, but perhaps such knowledge inspired the Martian heat rays in H. G. Wells’ 1897 science fiction novel War of the Worlds.

The Dawn of Electrical Machinery

In 1820 Hans Christian Ørsted discovered a relationship between electricity and magnetism. By 1879 inventors had exploited this relationship to launch what would become the electronics revolution of the twentieth century. A Natural Philosophy explains then-recent electromagnetic advances to its readers. Here, for example, Quackenbos shows how to magnetize a horseshoe-shaped piece of metal using a battery-powered electromagnet.

Making a permanent magnet using a battery-powered electromagnet.

Probably the most world-changing electrical technology of this time period was the telegraph. Telegraph networks provided worldwide instantaneous communication. For the first time in human history, messages could travel around the world in minutes instead of weeks. The textbook devotes several pages to describing the history, technology, and operation of telegraphs.

Further technological progress was on the horizon, but not quite in reach, due to the limitations of electric motors. Electric motors existed in 1879, but they were not useful for most applications due to the lack of an economical way to produce large amounts of electricity to drive them. Quackenbos explains:

A boat 28 feet long with a dozen persons on board has been propelled against the current at the rate of three miles an hour by electro-magnetic action. A locomotive engine has also been driven from ten to twelve miles an hour. But this is the utmost that has been effected, and in both cases the cost of keeping the galvanic battery in operation was much greater than that of producing an equivalent quantity of steam. […] Until these difficulties are removed, electro-magnetism can not be advantageously used as a mechanical agent.

It would take a few more decades before generators, turbines, and electrical grids advanced enough to make electric motors practical for industrial and domestic uses.

Surprises from Ultra-Powerful Magnets

In the section on scientific research using extremely powerful electromagnets, the author relates a discovery. Certain substances that had previously been thought to be magnetically inert actually show a slight reaction to sufficiently powerful magnetic field.

He describes any substance that is attracted by a magnet as magnetic and any that is repelled by a magnet as diamagnetic. I was surprised to learn something new when I read the following part:

Similar experiments may be made on liquids and gases by enclosing them in tubes. It is thus found that oxygen is magnetic; water, alcohol, ether, and the oils, diamagnetic.

Before reading that last sentence, I did not know that water was repelled by magnets! I had to look this up to confirm it is true. I later read about, and performed myself, an experiment in which I pushed a grape using a magnet. I still think it’s funny that I learned something about physics from a book over 140 years old!

Astronomical Measurements

It is interesting to compare what was known about astronomy in 1879 with our modern understanding. Pluto was not to be discovered until 1930, but all the major planets were known then.

I decided to compare the table of numbers shown below with modern values. Data about the planets show a mixture of impressive accuracy in some cases, and completely wrong values in others.

A table of then-current planetary data.

On the more accurate side are the distances of the planets from the Sun. By the 1770s, astronomers had measured the Solar System in terms of earthly distances by observing Venus passing between the Earth and Sun, as seen from different locations on the Earth. It is apparent that the calibration between celestial distances and earthly distances was a little bit off. All of the distances in the table are about 1.7% below the current values.

For the most part, the planet diameters are pretty good. As one might expect, the value for the Earth is the best. In fact, 7926 miles is also the exact modern value of the Earth’s equatorial diameter. Except for Mars and Neptune, the other planet diameters are within 4% of the correct values. Astronomers in 1879 thought Mars was 8% larger than it really is, and that Neptune was a whopping 19% larger than it really is. Neptune is so far away that it barely registers in a telescope, so I think we can go easy on them for that one.

What I can’t wrap my head around is how wrong some of the sidereal day values are. (The sidereal day of a planet is how long it takes for the planet to rotate once on its axis, with respect to distant stars.) For example, saying Venus rotates once every 23 hours, 16 minutes, and 19 seconds is not only completely wrong, it’s absurd!

First of all, Venus is completely covered by opaque white clouds. Venus always looks the same: completely white and blank. There is no way to see anything on its surface using optical telescopes from the Earth. But according to this textbook, apparently some early observers deluded themselves:

So intense is its brightness that variations in its surface (if indeed its surface is not hid from us by a cloudy atmosphere) for the most part escape detection, every portion of the disk being flooded with light. Yet spots have occasionally been seen on its surface, and mountains have been observed having an estimated height of from 15 to 20 miles.

I’m sorry, but nobody back then could see Venus rotating!

We now know, using spacecraft equipped with radar that can penetrate its dense and completely opaque atmosphere, that Venus rotates once every 243 days. Not only does it rotate very slowly, it does so in the opposite direction as most of the other planets. Seeing an utterly wrong value, with no objective basis, and with such precision (19 seconds!), just baffles me.

Quantum Hindsight

Sometimes we know that we don’t know something. Sometimes we don’t even suspect there is something to be known. It’s not clear which is the case when I read certain parts of A Natural Philosophy. A case in point: quantum mechanics. Although this book predates Max Planck’s quantum hypothesis, it is evident there were already clues leading in that direction. The section on optics includes this passage:

If solar light be analyzed with an instrument called the Spectroscope, a great number of dark lines, parallel to each other but differing in breadth, will be seen crossing its surface. The position of these lines is always the same in the solar spectrum; but, when a ray of star-light is decomposed, their number and arrangement are different, nor do they correspond in the case of different stars. The spectra of certain burning metals — iron, magnesium, sodium, zinc, copper, calcium, etc. — contain bright lines exactly corresponding to some of the dark lines in the spectra of the sun and stars. Now it is known that metallic vapors absorb the rays which they themselves emit; hence it is inferred that the atmospheres of the sun and stars contain the vapors of the metals in question, and that these metals are therefore incandescent on the surface of those heavenly bodies.

Absorption lines in stellar spectra are caused by electrons jumping between different quantum energy levels inside excited atoms. Although scientists knew about atoms in 1879, nobody then knew about subatomic particles like electrons. With no idea of electrons, and no quantum theory, there was no way to even begin to explain spectrum lines.

There is no mention of spectrum lines as a mystery to be solved. The author just states them as a fact. Perhaps this was a matter of economy; printed space in a text is limited, after all. It could be that he and others of his time didn’t imagine such things could ever be explained. It makes me wonder how curious Quackenbos was about things like this. Perhaps he thought, “that’s just the way things are.” Or maybe he wondered about them but kept speculations to himself.

I don’t want to be too smug. The same likely applies to us. In our own time, what subtle clues are we ignoring? What questions have we not yet even asked?

I can imagine someone 140 years from now flipping through a science textbook from our time. Commonplace knowledge for them will be beyond our imagination. I’d like to think they would appreciate our ingenuity. And just maybe, like I did, they will learn a thing or two.