What hourglass is made of
Measuring time with pouring sand.
- Two glass bulbs — has part. Glass vessels.
- Hourglass neck — has part. A narrow neck sets the rate.
- Hourglass wooden frame — has part. A protective frame.
- Gravity flow — uses. Sand pours through under gravity.
- Glass — is made of. Bulbs.
- Fine sand — is made of. Fine, uniform sand.