This Things of Science must be newer than the previous ones I posted. It isn’t numbered, The booklet too has gone from the larger 5″ x 6″ format to a narrower 3″ x 5″ (and nicely stapled now).
The “experiments” in this unit read more like math problems (not surprising, I suppose). But, again, like the best of Things of Science, the math is approached very practically — that is, by rolling dice, picking colored disks at random out of a box, etc. So it brings a very down-to-earth understanding of a complex topic.
This unit was also published earlier in 1962.
Here is the booklet:
More Things of Science scanned here.