| CHARLESSLAW | Principle involving the temperature and density of gases |
| DEGREES | They measure the temperature and seriousness of burns (7) |
| CLEARTHEAIR | Lower the temperature and reduce pollution? |
| ATMOSPHERE | The "standard" one of these takes into account vertical variations of pressure and density that may be determined for a given set of values at sea level. (10) |
| ALEXANDRIA | Home to ancient Wonder, dramatic rain and density in Amazon's character (10) |
| BOYLESLAW | Be slowly cracking up about a principle involving pressure of 27 |
| PLANCK | Physicist laying down principle involving speed of light |
| AVOGADROSLAW | The principle that equal volumes of all gases contain the same number of molecules at the same temperature and pressure (9,3) |
| WEIGHT | Boldness of a typeface or font; density of cloth; or, one of a series of blocks used with kitchen scales (6) |
| OSMIUM | It has the greatest density of the known elements |
| TEX | Unit of weight used to measure the density of textiles (3) |
| TESLA | The magnetic density of tales of woe? (5) |
| TAO | Chinese principle involving integrated wholeness |
| CANYON | Principle involving gluttony ultimately: gorge! (6) |
| TENEMENT | Principle involving guys in flat |
| ETHNIC | Moral principles involving any number of people |
| DALTON | Which chemist developed the law of partial pressure of gases and the atomic theory of matter? (6) |
| CAVENDISH | A famously eccentric and brilliant British scientist who discovered hydrogen and "weighed the world" - he was a master of gases, gravity, measures and might, yet so shy and reclusive he had an extra h |
| HYDROGEN | A colourless, odourless gas that has the lowest density of all gases (8) |
| SCHIEHALLION | 3,547ft conical-shaped mountain on which Maskelyne carried out experiments to determine the density of the earth |
