One of the fun things about The Book of Knowledge are the sections entitled “Things to Make and Things to Do”, which are filled with lots of crafts and games. (They also have some more serious instructions – including some basic first aid instructions, showing how to make splints for fractures.) I am having a lot of fun reading these sections because they contain knowledge that many times is largely forgotten or rarely used, but fun to know. So I have decided to start “republishing” some of the crafts and “how-to” instructions here. These are public domain, use them and the accompanying illustration(s) as you wish.
So, without further ado, here is “How to Measure the Diameter of a Ball” (The Book of Knowledge, 1919, pg. 6009.):
To measure the diameter of a ball exactly may not seem a very easy task, but there is a way of doing this which is quite simple. Take two blocks of wood, or two boxes, a little higher and wider than the ball, and stand these on a table with their sides pressed flush against a wall or against a larger box standing on a table. In between the two boxes or blocks place the ball as shown in this picture [shown below - B] and still keeping the sides flush against the wall, bring the two boxes together until the touch the ball.All we have to do now is to take a rule and measure the distance between the boxes, taking care, of course, to keep all the objects quite still and level. With the diameter thus accurately measured, we can obtain the other dimensions in the usual way, as, for instance, multiplying the diameter by 3.1416, or, roughly, 3 1/7, to get the circumference.