Darwin observed fossils of huge animals such as glyptodon why were these fossils of interest to him

I believe its is because the fossils of these animals looked like living species and they had a connection to the modern. A fossil is any preserved evidence of life from a past geological age, such as the impressions and remains of organisms embedded in stratified rocks. Fossils are created when organisms die, are in cased in dirt and rock, and are slowly replaced by minerals over time.

The speed of sound change as the sound of a boat engine moves down to the depths of the ocean The speed increases and then decreases as the temperature of the water increase. Sound do not travel faster in water than air due to the resistance. The salt and water molecules of the ocean cause interference for the sound wave to travel across it. It it had travel through air, then you can hear the sound of the incoming boat. But if it goes down into the water, and as you know it, going deeper into the water increases the pressure all the more that it muffles the sound of the engine of a boat. That is why it increases then decreases its sound as it goes down the ocean.