Exercise 1: sample answer

Edinburgh is far enough north that daylight varies a great deal through the year: in June the Sun is up for roughly seventeen hours, and in December for only about seven (check the figures). If daylight is always split into twelve parts, each June part is about 85 minutes long and each December part only about 35. So a seasonal hour in summer is more than twice as long as one in winter, which is why such hours stopped being practical once people wanted to compare times or use machines.