I chose the 26-inch Naval Observatory refractor as the likely model for the boys' drawing. But thanks to twitterer @jackdoerner I now know that this telescope had a twin. The McCormick telescope at the University of Virginia. They had been ordered at about the same time, but financial issues with both Leader McCormick and UVa meant that their telescope wasn't delivered and installed for another fifteen years. Ultimately, UVa had to rely on philanthropists to complete the funding of their project. Because of this delay the McCormick was never the biggest in the world, and was far less famous.
|The Naval Observatory 26-inch on the left.|
It's twin, University of Virginia's McCormick 26-inch on the right.
This story of twin telescopes and delays shouldn't have been at all surprising to me.
The telescope I'm most familiar with, Harvard's Great Refractor, also had a twin. And like these two 26 inch telescopes, the Harvard 15 inch telescope and its twin at the Pulkovo observatory near St. Petersburg Russia, were the largest in the world in their day too. Like the 26 inchers, there was a winner (Pulkovo), and an also-ran (Harvard). While Harvard wasn't ever really in contention to be the first, financial reasons nevertheless added delays in getting Harvard's 15 inch telescope pointed towards the sky. Harvard actually raised funds from astronomy enthusiasts to pay for their telescope. Donors got their names on a plaque that is still there today. (And they did it without kickstarter.)
It's almost like the 26 inch twins were twins of the 15 inch twins.
One of my biggest mistakes though was to assume that each telescope of this size was unique. I had believed that even our own Great Refractor at Harvard was unique, and had (for reasons I can't now pin down) assumed that Merz and Mahler had only made the lenses, and the telescopes at Harvard and Pulkovo were completely different. This assumption was completely wrong. Merz and Mahler made both 15 inch telescopes, and they look nearly identical. And Alvan Clark and Sons made both of the twin 26 inch telescopes, including the mounting.
This also shouldn't have been surprising, given that the telescope I get to actually use is an Alvan Clark nine-inch refractor made in 1912. (Sadly, the 15-inch Great Refractor at Harvard is non-functioning, and there are no funds available to restore it.) And I was perfectly aware of the fact that Clark made the entire telescope, as they did with countless others.
Incidentally, Avlan Clark and Sons' ascendancy as the preeminent telescope makers of their day was very rapid. in the mid 1840s Alvan and his sons began making a few basic reflector and refractor telescopes, more or less as a hobby at first, while Alvan continued his career as a painter and engraver. After a few small successes, Alvan Clark Sr. had an opportunity to look through none other than Harvard's Great Refractor, shortly after it was installed. Based on what he had learned to that point, he saw minor problems with the telescope and decided he could do a better job. Plus, he found out how much these lenses cost —the Harvard lens was $12,000 in 1844, which would be about $300,000 today). He turned his hobby into a business, and in just over ten years was given the opportunity to build the largest telescope in the world, an 18.5 inch telescope commissioned by the University of Mississippi (but eventually sold to the University of Chicago in 1862, as the Civil War made the original deal impossible). His firm continued to dominate the field right up to the end of the refractor era, making four of the final six record-breakers, including the last two at 36 and 40 inches.
So the two 26 inch telescopes are very much twins. Even the distinctive mount, which was also designed and built by George Basset Clark. This is particularly notable given the fact that telescopes in different locations might need different mounting hardware. The angle of the mount has to parallel the axis of the Earth, and if latitudes are very different, different hardware might be needed. But in this case, both telescopes were designed for nearly the same latitude (less than one degree apart), which makes it almost trivial for them to share the same mounting hardware.
So which one is the inspiration? Or was it another telescope entirely? Again, I have no firm answers. But this is where it gets really interesting. @jackdoerner also pointed out that the Viriginia telescope was operational in Cambridge (Massachusetts) prior to its installation. When I assumed that Clark only made the lens, this would have been unimaginable. But the evidence is there to confirm what twitter was telling me. In 1877, the Naval Observatory discovered the moons of Mars, Deimos and Phobos, using their 26-inch telescope. They quickly got word out to other important sites to confirm their finding. And one of the sites they contacted was the Cambridge telescope factory, where the still undelivered McCormick 26-inch telescope was used to confirm the moons.
This is notable, because in the last article, I wondered if the boys had ever visited the 26-inch in Washington D.C. But this new information means that its twin was only 100 miles away instead of 500 miles. Did they ever visit Alvan Clark and Sons' factory? Their ages probably make this impossible, but I can't say for sure because I don't know their ages. The books were written roughly from 1892 to 1895. The telescope was delivered to Virginia in 1885. If the boys were teens when they wrote the books, then they might have been too young to visit the telescope in Cambridge and draw it with so much accuracy.
I'm also still guessing that Alvan Clark and Sons didn't provide the pier itself (the brick structure). But their clock drive design would likely have mandated some sort of a pier where the mechanism could be inside the pier, and would need to be accessed. So while the piers are clearly not identical, they are clearly similar, and either could have been the inspiration for that drawing.
It still is most likely one of these two telescopes. Alvan Clark and Sons did make smaller telescopes that used a similar mount, but I haven't found any where the counterweights looked anything like these two telescopes. It's unlikely the boys saw the McCormick telescope in Cambridge because of the timing. And it's even more unlikely they'd ever see a picture of the McCormick—I haven't found a single image from the 19th century yet. I'm sticking with one of these being correct, and the Naval telescope remains the strong favorite.
Unless of course the Internet tells me otherwise.