Full Idea
'Uranium lumps have mass of less than 1000 kg' is a law, but 'gold lumps have mass of less than 1000kg' is not a law.
Clarification
A lump of uranium that big would explode
Gist of Idea
'All uranium lumps are small' is a law, but 'all gold lumps are small' is not
Source
Alexander Bird (Philosophy of Science [1998], Ch.1)
Book Reference
Bird,Alexander: 'Philosophy of Science' [UCL Press 2000], p.28
A Reaction
A nice example. Essentialists talk about the nature of the substances; regularity theorists prefer to talk of nested or connected regularities (e.g. about explosions). In induction, how do you decide what your duty requires you to observe?