Why all the buried glass, always something with this place!

As we clear more land I often find broken glass buried under the top later or so of soil. Always in the same maybe 50' or so square area. I wonder if a past owner had a greenhouse there and then buried it rather than disposing if it fell into disrepair. I know that prior to our purchase an older couple had this as a summer home. prior to them it sounds like a farmy type family or couple was here. According to our elderly neighbor that family had a small orchard and garden. That is the 5 heritage apple trees, some in better shape than others, we still have now. Did they have a greenhouse just off the orchard that is where this glass is buried. By the time we moved here it had all gone to woodland and I didn't discover this buried glass issue until we started clearing and expanding for the chickens and then the orchard. I've unearthed quite a bit of glass over the last several years and occasionally a new spot is found by the chickens scratching. I'm so glad that none have been hurt by it as far as know. Today I found another big area of glass buried when I pulled up some bramble by the roots. It was tedious to uncover and pick out. Once done I had a 6 gallon bucket nearly full of glass pieces. The birds of course were nosy about what I was doing and I had to keep shooing them away as I uncovered more and more glass. It's always something. This house and land has been  lot of hard work but I try my best these days. I've gotten a lot done as the kids have grown up and I have more time. It does sometimes feel like one step forward two steps back but there is progress.