纪录片《大英博物馆世界简史》 062希伯来星盘（3）（在线收听）

"Little Lewis, I have perceived well thy ability to learn sciences touching numbers and proportions, and I have also considered thy earnest prayer specially to learn the treatise of the astrolabe. Here is an astrolabe of our horizon, and a little treatise to teach a certain number of conclusions appertaining to the same instrument.

"Trust well that all the conclusions that can be found, or else possibly might be found, in so noble an instrument as an astrolabe, are not perfectly understood by any mortal man in this region, and I have seen that there be some instructions that will not in all things deliver their intended results; and some of them be too hard for thy tender age of ten year to understand."

I have to say that I find it as difficult to grapple with an astrolabe as little Lewis at the age of ten. It is so fiendishly clever and complicated in its structure, and it contains so much information, that it would take me the whole of this programme to describe it fully. So what follows is very summary indeed.