Across
1
Preserved remains of ancient life
5
Curved glass that refracts light
6
Disturbance that transfers energy
8
Naturally occurring inorganic solid
10
Nerve cell in the brain
11
Ball of burning gas in space
12
Force that attracts objects together
Down
2
Infectious microscopic agent
3
Second lightest element
4
Gas essential for breathing
7
Chemical element in table salt
9
Precious yellow metallic element