liquid-in-glass thermometer:

A liquid-in-glass thermometer has a bulb with a long capillary tube of uniform and fine bore. A suitable liquid is filled in the bulb. When the bulb contacts a hot object, the liquid in it expands and rises in the tube. The glass stem of a thermometer is thick and acts as a cylindrical lens. This makes it easy to see the liquid level in the glass tube.

Uses:

Thus, mercury is one of the most suitable thermometric materials. The mercury-in-glass thermometer is widely used in laboratories, clinics, and houses to measure temperature in the range from -10°C to 150°C.