Tunnels 01, Tunnels

the way to the fridge, he stopped to examine something lying to the side. "What's this?"
    It was a package neatly wrapped in brown paper.
    "It's addressed to Dad. I think we should open it," he said without a moment's hesitation, snatching up a dirty butter knife left on a plate by the sink. Cutting into the brown paper, he excitedly tore open the cardboard box inside, then ripped away a cocoon of bubble wrap to reveal a luminous sphere, glowing from its time in the darkness.
    He held it up before him, his eyes sparkling with both excitement and the waning light emanating from the sphere. It was the object he'd read about in his father's journal.
    Rebecca had stopped reading the telephone bill and had risen to her feet. She was looking at the sphere intently.
    "There's a letter in here as well," Will said, reaching into the ravaged cardboard box.
    "Here, let me see it," Rebecca said, her hand snaking toward the box. Will took a step back, holding the sphere in one hand while he shook open the letter with the other. Rebecca withdrew her hand and sat back down, watching her brother's face carefully as he leaned on the counter by the sink and began to read the letter aloud. It was from UniversityCollege's physics department.

    Dear Roger,
    It was wonderful to hear from you again after all these years -- it brought back warm memories of our time together at college. It was also good to catch up on your news --Steph and I would love to visit when convenient.
    As regards the item, I apologize for taking so long to respond, but I wanted to be sure I had collated the results from all concerned. The upshot is that we are well and truly stumped.
    As you specified, we did not breach or penetrate the glass casing of the sphere, so all our tests were noninvasive in nature.
    On the matter of the radioactivity, no harmful emissions registered when it was tested -- so at least I can put your mind at rest on that one.
    A metallurgist carried out an MS on a microscopic shaving from the base of the metal cage, and he agreed with your view that it's Georgian. He thinks the cage is made out of pinchbeck, which is an alloy of copper and zinc invented by Christopher Pinchbeck (1670 - 1732). It was used as a substitute for gold and only produced for a short while. Apparently, the formula for this alloy was lost when the inventor's son, Edward, died. He also told me that genuine examples of this material are scarce, and it's hard to find an expert who can give an unequivocal identification. Unfortunately, I haven't yet been able to get the cage carbon dated to confirm its precise age -- maybe next time?
    What is particularly interesting is that an x-ray revealed a small, free-floating particle in the center of the sphere itself that does not alter its position even after rigorous agitation -- this is puzzling, to say the least. Moreover, from a physical inspection, we agree with you that the sphere appears to be filled with two distinct liquid factions of differing densities. The turbulence you noted in these factions does not correspond to temperature variations, internal or external, but is unquestionably photoreactive -- it only seems to be affected by a lack of light!
    Here's the rub: The crew over in the chemistry department have never seen anything like it before. I had a fight on my hands to get it back from -- they were dying to crack the thing open in controlled conditions and run a full analysis. They tried spectroscopy when the sphere was at its brightest (at maximum excitation its emissions are in the visible spectrum -- in layman's terms, not far off daylight, with a level of UV within acceptable safety parameters, and the "liquids" appeared to be predominately helium -- and silver-based. We can't make any more progress on this until you allow us to open it.
    One hypothesis is that the solid particulate at the center may be acting as a catalyst for a reaction that is triggered by the absence of light. We can't confirm how, at this juncture, or come up with any comparable reactions that would occur over such a long period of time, assuming the sphere really does date from the Georgian era. Remember, helium was not discovered until 1895 -- this is at odds with our estimate for the date of the metal casing.
    In short, what we have here is a conundrum. We would all very much welcome a visit from you for a multifaculty meeting so that we can schedule a program for further analysis of the item. It may even be useful for some of our