Double temperature measurement with an arduino

Double temperature measurement

How does a material like cotton wool act as a heat insulator? For this little experiment in school lessons you only need an Arduino, two 10k ntc resistors and two 10k resistors.
Surely I could have built this small gauge into a housing, but sometimes even students find it interesting to really see technology.

Part of the circuit diagram is shown in the picture. Unfortunately, the hcmax7219 is not in the library for the program Fritzing. Therefore, I have described the wiring for the display in the ino file.