Dear John, Yes, Eratosthenes was a great man who is also noted for his sieve for extracting prime numbers.
This may not be the right list for asking about the performance of camels but I am intrigued that it took a camel 50 days to travel from Aswan to Alexandria. The straight line distance is a little over 500 miles and I can well imagine that the route was far from straight. Using "one day's travel" as a unit of distance was pretty much the only way of estimating differences in longitude for many centuries after Eratosthenes. A variant of this is used when training people in the sport of orienteering... You stand a trainee on open heathland and ask him to stick his pencil in the ground. Then using a compass you ask him to pace out 100 steps north, 100 steps east, 100 steps south and then 100 steps west and pick up the pencil! I have read that when Columbus was making preparations for his well-known 1492 trip he estimated the longitude of Japan relative to Spain by noting how long it took to get to Japan by the silk route using horses, mules and so on. Subtracting this from 360 he estimated how many degrees of longitude Japan was west of Spain and hence the distance. This was about 3000 modern miles which is a gross under-estimate caused by grossly over-estimating how far east Japan was. That said, he duly sailed about 3000 miles, spotted land, and decided he had got to Asia. Some of this story seems plausible. It would be good if it were also true! All the best Frank --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
