Here it is appropriate to mention an aspect of Galileo’s scientific work that became very prominent somewhat later. This is the importance of precise measurement, already evident in La Bilancetta. It was probably in 1588-89 that Galileo began to reflect on the nature of measurement and its vital role in science. Now it’s one thing to prove proportionality mathematically- as that bodies of the same specific weight have their weights proportional to their volumes- and it is another thing to verify this in fact.

You tell me you would like to know the device by which I was able to assure myself that the vertically falling  body leaving from the rest passed 100 braccia of height in five seconds. Here two things are sought: the first is the time of descent through 100 braccia, and the second is to find what part that time is of 24 hours in the [del primo mobile].

His life (George Graham's) is of particular interest to astronomers because of the part he played in the progress of their science. Although, by 1700, the telescope had increased astronomical knowledge by many discoveries, it was obvious that more accurate instruments had to be devised before further advance could be attained. Necessary mechanical improvements were furnished by George Graham ans others of his time.

To qualify for the highest award of £20,000, the timekeeper would have to show that on arrival in Jamaica it had not exceeded a total loss or gain of 1 minute 54 seconds of time since it had been set by Mr Robertson at Portsmouth on 7 November, some 81 days previously. This performance would be the equivalent of a variation of under 1 1/2 seconds a day, a standard of timekeeping which, even to-day,could be achieved by very few high grade watches.

“’I have such a time- measurer that if 4 or 6 examples of this instrument were constructed, and if they were allowed to operate at the same time, we would find that in confirmation of their accuracy, the times measured and indicated by these time-measurers would show differences of only one second, not only from hour to hour, but from day to day and from month to month, so uniform would be their operation; these clocks are really admirable for the observers of motion and celestial phenomenon, and in addition, their constructio