I want to know the answer to the following question:
What series of books does Gray say Bell would go to sleep reading?
All the background I'm provided with is that "Bell's inventions spanned a wide range of interests and included a metal jacket to assist in breathing, the audiometer to detect minor hearing problems, a device to locate icebergs, investigations on how to separate salt from seawater, and work on finding alternative fuels.". Is that enough to answer the question?